[reclient] Add nacl toolchain config to reclient

We need some tweaks for nacl compilations - particularly, it requires
manually setting some inputs that can't easily be found programmatically.

Unfortunately, there isn't an easy way of deferring evaluation of
$cc_rewrapper, so I had to move it to gcc_toolchain.

Change-Id: I233451e7f482859a3907b45f5be7ffe13197fb30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2693029
Commit-Queue: Rubens Farias <rubensf@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#854290}
GitOrigin-RevId: 3ea7cd70127c43f62b328b85c672d5296accd087
1 file changed