crossgcc: Fix compilation on Clang systems

Most cross compilers fail to compile on systems with Clang being the
default compiler (OS X and some BSDs). Clang dislikes some of GCC's
autogenerated code. We also missed switching CFLAGS to CXXFLAGS when GCC
switched to C++ compilation per default.

Change-Id: I87caa1a15982c431048aa79748ea7ef655a9a3a1
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/14232
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed