[Driver] Fix driver support for color diagnostics

Diagnostics that happen during driver time do not have color output support
unless -fcolor-diagonostic is explicitly passed into the driver.  This is not a
problem for cc1 since dianostic arguments are properly handled and color is
enabled by default if the terminal supports it.

Make the driver behave like CC1. There are tests that already check for these
flags, but for the color itself there's no sensible way to test it.

Differential Revision: http://reviews.llvm.org/D20404

rdar://problem/26290980

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@271042 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 515ac7a1d5c47c0c2d3506191197344f1f54092d)
3 files changed