Fix gclient crash with unicode strings in .gclient files.
Fix gclient crash with unicode strings in .gclient files.

Older .gclient files might have explicit u'' strings in their
specs; as part of upgrading code to Python3 compatibility,
we apparently recently introduced a bug in the handling of this
that might cause them to fail on Windows.

This CL fixes that issue by ensuring that the GIT_DIR env var
is always set to a regular string, regardless of whether
the solution name was specified to be a regular string
or a unicode string.

Bug: 1016599
Change-Id: I295d220559eac20a2ced876672d5ccdb787a5338
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1874704
Reviewed-by: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Commit-Queue: Dirk Pranke <6693ee08b084bb2ffa767f664c99b689395e0e4b@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools