Set Perl search path more idiomatically

Back in commits 1df92eea, f884a968, and 592123ef I used some
hackish code to set the script search path, unaware despite decades of
perl that there was a completely standard way to do this. This patch
changes those cases to use the standard perl FindBin package.

src/backend/catalog/genbki.pl

@@ -17,9 +17,8 @@ use strict;
 use warnings;
 use Getopt::Long;
 
-use File::Basename;
-use File::Spec;
-BEGIN { use lib File::Spec->rel2abs(dirname(__FILE__)); }
+use FindBin;
+use lib $FindBin::RealBin;
 
 use Catalog;
 

src/tools/msvc/build.pl

@@ -5,9 +5,8 @@
 use strict;
 use warnings;
 
-use File::Basename;
-use File::Spec;
-BEGIN { use lib File::Spec->rel2abs(dirname(__FILE__)); }
+use FindBin;
+use lib $FindBin::RealBin;
 
 use Cwd;
 

src/tools/msvc/install.pl

@@ -6,9 +6,8 @@
 use strict;
 use warnings;
 
-use File::Basename;
-use File::Spec;
-BEGIN { use lib File::Spec->rel2abs(dirname(__FILE__)); }
+use FindBin;
+use lib $FindBin::RealBin;
 
 use Install qw(Install);
 

src/tools/msvc/mkvcbuild.pl

@@ -7,9 +7,8 @@
 use strict;
 use warnings;
 
-use File::Basename;
-use File::Spec;
-BEGIN { use lib File::Spec->rel2abs(dirname(__FILE__)); }
+use FindBin;
+use lib $FindBin::RealBin;
 
 use Mkvcbuild;
 

src/tools/msvc/vcregress.pl

@@ -12,8 +12,9 @@ use File::Basename;
 use File::Copy;
 use File::Find ();
 use File::Path qw(rmtree);
-use File::Spec;
-BEGIN { use lib File::Spec->rel2abs(dirname(__FILE__)); }
+
+use FindBin;
+use lib $FindBin::RealBin;
 
 use Install qw(Install);