[analyzer] Add --override-compiler option to scan-build.

The new advanced option ensures ccc-analyze is used even when better
interposition methods are available.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182981 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Always use ccc-analyzer when running scan-build on buildbot

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182982 91177308-0d34-0410-b5e6-96231b3b80d8