perl-5.12.1: Add errno fix from perl-5.18.2

Avoid error

    ext/Errno/t/Errno..............................................FAILED--Further testing stopped: No errno's are exported
    make: *** [makefile:874: test] Error 29

by adding a fix from perl-5.18.2.

perl-5.12.1-0.build.sh

@@ -70,6 +70,14 @@ test -e perl-$VERSION.tar.gz || wget http://www.cpan.org/src/5.0/perl-$VERSION.t
 test -d perl-$VERSION || tar xf perl-$VERSION.tar.gz
 cd perl-$VERSION
 
+# Note: make test below would fail with:
+#     ext/Errno/t/Errno ........... FAILED--Further testing stopped: No errno's are exported
+# Cure:
+# https://rt.perl.org/Public/Bug/Display.html?id=123784
+#   ... caused by a change in GCC 5.0's preprocesor
+#   ... Simple work-around is to call the preprocessor with -P option
+sed -i -e '/"$cppstdin $Config/ s/cppstdin/cppstdin -P/' ext/Errno/Errno_pm.PL
+
 # -d : use defaults for all answers.
 # -e : go on without questioning past the production of config.sh.
 # -s : silent mode, only echoes questions and essential information.