gcc was unable to find zlib.h, so use CPPFLAGS insteaf

of CFLAGS (thanks Romain and Kazuhiko)

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@41877 20353a03-c40f-0410-a6d1-a30d3c3de9de

buildout/software-profiles/libpng.cfg

@@ -10,5 +10,5 @@ recipe = hexagonit.recipe.cmmi
 url = http://download.sourceforge.net/libpng/libpng-1.4.4.tar.gz
 md5sum = 297b38f925e745061489b41b1f7c4bb1
 environment =
-  CFLAGS =-I${zlib:location}/include
+  CPPFLAGS =-I${zlib:location}/include
   LDFLAGS =-L${zlib:location}/lib -Wl,-rpath -Wl,${zlib:location}/lib