Don't copy CFLAGS from portage's make.conf to .pc

--- a/chardet.pc.in
+++ b/chardet.pc.in
@@ -9,4 +9,4 @@ Name: @PACKAGE_NAME@
 Description: Mozilla's Universal Charset Detector C/C++ API
 Version: @PACKAGE_VERSION@
 Libs: -L${libdir} -lchardet
-Cflags: -I${includedir}/chardet @CFLAGS@
+Cflags: -I${includedir}/chardet