perl: Override cpprun configuration symbol

This will not change any existing packages' functionality. All packages
that used this symbol before during build(with it's value being "cc  -E") most
likely would've failed compilation.
Note that this change is only in effect during build.

Signed-off-by: Marcel Denia <naoir@gmx.net>

lang/perl/perlmod.mk

@@ -55,7 +55,7 @@ define perlmod/Configure
 	(cd $(if $(3),$(3),$(PKG_BUILD_DIR)); \
 	PERL_MM_USE_DEFAULT=1 \
 	$(2) \
-	$(PERL_CMD) Makefile.PL \
+	$(PERL_CMD) -MConfig -e '$$$${tied %Config::Config}{cpprun}="$(GNU_TARGET_NAME)-cpp -E"; do "Makefile.PL"' \
 		$(1) \
 		AR=ar \
 		CC=$(GNU_TARGET_NAME)-gcc \