Split `gclient sync` into separate `gclient sync --nohooks` and
`gclient runhooks` steps so that we can optionally apply patches
from `runhooks.patch` in-between. This is necessary because the
src/tools/clang/scripts/update.py script is run via a hook and has
dependencies on the VS toolchain scripts which must be patched to
properly consider the GYP_MSVS_VERSION environment variable.
Marshall Greenblatt