crossgcc: Add clang support

Add a new option -C|--clang to buildgcc to build a clang based
toolchain as opposed to a gcc based toolchain. This toolchain
comes with the required patches needed to successfully build
coreboot, and also with clang's famous scan-build script.

Change-Id: I1aea7cd6002edc4f3bb2b46dc1f69a212ad18f77
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/10415
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/util/crossgcc/sum/clang-tools-extra-3.6.1.src.tar.xz.cksum b/util/crossgcc/sum/clang-tools-extra-3.6.1.src.tar.xz.cksum
new file mode 100644
index 0000000..17d55cb
--- /dev/null
+++ b/util/crossgcc/sum/clang-tools-extra-3.6.1.src.tar.xz.cksum
@@ -0,0 +1 @@
+d93136f56999d8ae1ffebb9cd0cd7f3c27ba77c4  tarballs/clang-tools-extra-3.6.1.src.tar.xz