install_toolchain: fix variable quoting & braces.

Incorporate review feedback comments from
https://chromium-review.googlesource.com/#/c/444043/

BUG=None
TEST='Locally modified go version check to use
cross_get_version_or_die(), ran the script to verify.'

Change-Id: Ie0c131f39d1ad5b825c49eea7913ab2da8a2a3d3
Reviewed-on: https://chromium-review.googlesource.com/446018
Commit-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed