Make some fixes to allow building Postgres on macOS 10.14 ("Mojave").

Apple's latest rearrangements of the system-supplied headers have broken
building of PL/Perl and PL/Tcl.  The only practical way to fix PL/Tcl is to
start using the "-isysroot" compiler flag to point to SDK-supplied headers,
as Apple expects.  We must also start distinguishing where to find Perl's
headers from where to find its shared library; but that seems like good
cleanup anyway.

Extensions that formerly did something like -I$(perl_archlibexp)/CORE
should now do -I$(perl_includedir)/CORE instead.  perl_archlibexp
is still the place to look for libperl.so, though.

If for some reason you don't like the default -isysroot setting, you can
override that by setting PG_SYSROOT in configure's arguments.  I don't
currently think people would need to do so, unless maybe for cross-version
build purposes.

In addition, teach configure where to find tclConfig.sh.  Our traditional
method of searching $auto_path hasn't worked for the last couple of macOS
releases, and it now seems clear that Apple's not going to change that.
The workaround of manually specifying --with-tclconfig was annoying
already, but Mojave's made it a lot more so because the sysroot path now
has to be included as well.  Let's just wire the knowledge into configure
instead.  To avoid breaking builds against non-default Tcl installations
(e.g. MacPorts) wherein the $auto_path method probably still works,
arrange to try the additional case only after all else has failed.

Back-patch to all supported versions, since at least the buildfarm
cares about that.  The changes are set up to not do anything on macOS
releases that are old enough to not have functional sysroot trees.

config/tcl.m4

@@ -13,6 +13,10 @@ fi
 
 # PGAC_PATH_TCLCONFIGSH([SEARCH-PATH])
 # ------------------------------------
+# If the user doesn't specify $TCL_CONFIG_SH directly, search for it in
+# the list of directories passed as parameter (from --with-tclconfig).
+# If no list is given, try the Tcl shell's $auto_path.
+
 AC_DEFUN([PGAC_PATH_TCLCONFIGSH],
 [AC_REQUIRE([PGAC_PATH_TCLSH])[]dnl
 AC_BEFORE([$0], [PGAC_PATH_TKCONFIGSH])[]dnl
@@ -24,7 +28,14 @@ if test -z "$TCL_CONFIG_SH"; then
     set X $pgac_test_dirs; shift
     if test $[#] -eq 0; then
         test -z "$TCLSH" && AC_MSG_ERROR([unable to locate tclConfig.sh because no Tcl shell was found])
-        set X `echo 'puts $auto_path' | $TCLSH`; shift
+        pgac_test_dirs=`echo 'puts $auto_path' | $TCLSH`
+        # On newer macOS, $auto_path frequently doesn't include the place
+        # where tclConfig.sh actually lives.  Append that to the end, so as not
+        # to break cases where a non-default Tcl installation is being used.
+        if test -d "$PG_SYSROOT/System/Library/Frameworks/Tcl.framework" ; then
+            pgac_test_dirs="$pgac_test_dirs $PG_SYSROOT/System/Library/Frameworks/Tcl.framework"
+        fi
+        set X $pgac_test_dirs; shift
     fi
 
     for pgac_dir do

configure

@@ -668,6 +668,7 @@ python_majorversion
 PYTHON
 perl_embed_ldflags
 perl_embed_ccflags
+perl_includedir
 perl_useshrplib
 perl_privlibexp
 perl_archlibexp
@@ -9773,6 +9774,14 @@ You might have to rebuild your Perl installation.  Refer to the
 documentation for details.  Use --without-perl to disable building
 PL/Perl." "$LINENO" 5
   fi
+  # On most platforms, archlibexp is also where the Perl include files live ...
+  perl_includedir="$perl_archlibexp"
+  # ... but on some macOS versions, we must look under $PG_SYSROOT instead
+  if test x"$PG_SYSROOT" != x"" ; then
+    if test -d "$PG_SYSROOT$perl_archlibexp" ; then
+      perl_includedir="$PG_SYSROOT$perl_archlibexp"
+    fi
+  fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for CFLAGS recommended by Perl" >&5
 $as_echo_n "checking for CFLAGS recommended by Perl... " >&6; }
@@ -18306,7 +18315,14 @@ if test -z "$TCL_CONFIG_SH"; then
     set X $pgac_test_dirs; shift
     if test $# -eq 0; then
         test -z "$TCLSH" && as_fn_error $? "unable to locate tclConfig.sh because no Tcl shell was found" "$LINENO" 5
-        set X `echo 'puts $auto_path' | $TCLSH`; shift
+        pgac_test_dirs=`echo 'puts $auto_path' | $TCLSH`
+        # On newer macOS, $auto_path frequently doesn't include the place
+        # where tclConfig.sh actually lives.  Append that to the end, so as not
+        # to break cases where a non-default Tcl installation is being used.
+        if test -d "$PG_SYSROOT/System/Library/Frameworks/Tcl.framework" ; then
+            pgac_test_dirs="$pgac_test_dirs $PG_SYSROOT/System/Library/Frameworks/Tcl.framework"
+        fi
+        set X $pgac_test_dirs; shift
     fi
 
     for pgac_dir do
@@ -18355,7 +18371,7 @@ fi
 # check for <perl.h>
 if test "$with_perl" = yes; then
   ac_save_CPPFLAGS=$CPPFLAGS
-  CPPFLAGS="$CPPFLAGS -I$perl_archlibexp/CORE"
+  CPPFLAGS="$CPPFLAGS -I$perl_includedir/CORE"
   ac_fn_c_check_header_compile "$LINENO" "perl.h" "ac_cv_header_perl_h" "#include <EXTERN.h>
 "
 if test "x$ac_cv_header_perl_h" = xyes; then :

configure.in

@@ -1044,6 +1044,15 @@ You might have to rebuild your Perl installation.  Refer to the
 documentation for details.  Use --without-perl to disable building
 PL/Perl.])
   fi
+  # On most platforms, archlibexp is also where the Perl include files live ...
+  perl_includedir="$perl_archlibexp"
+  # ... but on some macOS versions, we must look under $PG_SYSROOT instead
+  if test x"$PG_SYSROOT" != x"" ; then
+    if test -d "$PG_SYSROOT$perl_archlibexp" ; then
+      perl_includedir="$PG_SYSROOT$perl_archlibexp"
+    fi
+  fi
+  AC_SUBST(perl_includedir)dnl
   PGAC_CHECK_PERL_EMBED_CCFLAGS
   PGAC_CHECK_PERL_EMBED_LDFLAGS
 fi
@@ -2229,7 +2238,7 @@ fi
 # check for <perl.h>
 if test "$with_perl" = yes; then
   ac_save_CPPFLAGS=$CPPFLAGS
-  CPPFLAGS="$CPPFLAGS -I$perl_archlibexp/CORE"
+  CPPFLAGS="$CPPFLAGS -I$perl_includedir/CORE"
   AC_CHECK_HEADER(perl.h, [], [AC_MSG_ERROR([header file <perl.h> is required for Perl])],
                   [#include <EXTERN.h>])
   # While we're at it, check that we can link to libperl.

contrib/hstore_plperl/Makefile

@@ -39,4 +39,4 @@ endif
 # last, probably because it sometimes contains some header files with names
 # that clash with some of ours, or with some that we include, notably on
 # Windows.
-override CPPFLAGS := $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_archlibexp)/CORE
+override CPPFLAGS := $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_includedir)/CORE

contrib/jsonb_plperl/Makefile

@@ -39,4 +39,4 @@ endif
 # last, probably because it sometimes contains some header files with names
 # that clash with some of ours, or with some that we include, notably on
 # Windows.
-override CPPFLAGS := $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_archlibexp)/CORE
+override CPPFLAGS := $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_includedir)/CORE

src/Makefile.global.in

@@ -331,6 +331,7 @@ else
 endif
 perl_archlibexp		= @perl_archlibexp@
 perl_privlibexp		= @perl_privlibexp@
+perl_includedir		= @perl_includedir@
 perl_embed_ccflags	= @perl_embed_ccflags@
 perl_embed_ldflags	= @perl_embed_ldflags@
 

src/pl/plperl/GNUmakefile

@@ -16,7 +16,7 @@ endif
 # probably because it sometimes contains some header files with names
 # that clash with some of ours, or with some that we include, notably on
 # Windows.
-override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_archlibexp)/CORE
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_includedir)/CORE
 
 rpathdir = $(perl_archlibexp)/CORE
 

src/template/darwin

@@ -3,6 +3,18 @@
 # Note: Darwin is the original code name for macOS, also known as OS X.
 # We still use "darwin" as the port name, partly because config.guess does.
 
+# Select where system include files should be sought.
+if test x"$PG_SYSROOT" = x"" ; then
+  PG_SYSROOT=`xcodebuild -version -sdk macosx Path 2>/dev/null`
+fi
+if test x"$PG_SYSROOT" != x"" ; then
+  if test -d "$PG_SYSROOT" ; then
+    CPPFLAGS="$CPPFLAGS -isysroot $PG_SYSROOT"
+  else
+    PG_SYSROOT=""
+  fi
+fi
+
 # Select appropriate semaphore support.  Darwin 6.0 (macOS 10.2) and up
 # support System V semaphores; before that we have to use named POSIX
 # semaphores, which are less good for our purposes because they eat a