Try to run empty test program before running any real AC_TRY_RUN's, to

prevent disguised failures.

configure.in

@@ -943,6 +943,22 @@ if test x"$pgac_cv_var_int_optreset" = x"yes"; then
   AC_DEFINE(HAVE_INT_OPTRESET, 1)
 fi
 
+
+# This test makes sure that run tests work at all.  Sometimes a shared
+# library is found by the linker, but the runtime linker can't find it.
+# This check should come after all modifications of compiler or linker
+# variables, and before any other run tests.
+AC_MSG_CHECKING([test program])
+AC_TRY_RUN([int main() { return 0; }],
+[AC_MSG_RESULT(ok)],
+[AC_MSG_RESULT(failed)
+AC_MSG_ERROR([[
+*** Could not execute a simple test program.  This may be a problem
+*** related to locating shared libraries.  Check the file 'config.log'
+*** for the exact reason.]])],
+[AC_MSG_RESULT([cross-compiling])])
+
+
 dnl Check to see if we have a working 64-bit integer type.
 dnl This breaks down into two steps:
 dnl (1) figure out if the compiler has a 64-bit int type with working