build_packages: Don't transitively upgrade critical SDK packages

Toolchain packages should only be upgraded on the build host by
`cros_setup_toolchains`, but are currently being upgraded as a result
of being in the transitive depgraph of build targets due to BDEPEND.
gcc and glibc are the most problematic packages being rebuilt to this
and are both not installed via Portage to board targets, so are safe to
hardcode in this manner while we find a better solution to the overall
problem.

BUG=chromium:1050752
TEST=`build_packages`

Change-Id: I2b0bfc4d2b18b7ac5fb24d776fee079463c8f08e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1967866
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed