Introduced EXTRA_CFLAGS as an environment variable used by the Makefile. Meant
to be used for flags that change binary compatibility.
Distutils was tweaked to also use the variable if used during compilation of
the interpreter.
diff --git a/Makefile.pre.in b/Makefile.pre.in
index e4d9008..7b440f3 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -55,7 +55,7 @@
# Compiler options
OPT= @OPT@
BASECFLAGS= @BASECFLAGS@
-CFLAGS= $(BASECFLAGS) $(OPT)
+CFLAGS= $(BASECFLAGS) $(OPT) $(EXTRA_CFLAGS)
# Both CPPFLAGS and LDFLAGS need to contain the shell's value for setup.py to
# be able to build extension modules using the directories specified in the
# environment variables