llvm_tools: get_patch.py now applies patches

This commit gives get_patch.py the ability to actually
write and apply patches to the source tree.

BUG=b:318755454
TEST=run_tests_for.py llvm_tools/get_patch.py

Change-Id: I32d749f0f11b284151343f247a57d57bce2c1c32
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5171747
Reviewed-by: George Burgess <gbiv@chromium.org>
Commit-Queue: Jordan Abrahams-Whitehead <ajordanr@google.com>
Tested-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
2 files changed