Squashed 'site_scons/' changes from 89f0bb7..2b57224

2b57224 Allow general and wild-card specification of a toolchain

git-subtree-dir: site_scons
git-subtree-split: 2b572242cbf15a49e7ae730e08756898d3c8996a
Merge commit '300fc1a7e391dcc9f0f37ccdbcbf17593e9fc84a'