Ports: Export CC with added --sysroot for building Python

This is used in the setup.py file when adding include and lib paths to
the list when crosscompiling, if it's not found in any of the checked
environment variables they don't get added.

Ports/python3/package.sh

@@ -19,6 +19,7 @@ depends="libffi zlib"
 # FIXME: --enable-optimizations results in lots of __gcov_* linker errors
 configopts="--disable-ipv6 --without-ensurepip ac_cv_file__dev_ptmx=no ac_cv_file__dev_ptc=no"
 
+export CC="${CC} --sysroot=${SERENITY_INSTALL_ROOT}"
 export BLDSHARED="${CC} -shared"
 
 pre_configure() {