build: print a warning message for Reclient deprecation

Some external projects still use Reclient, which fail with
the assertion `!(use_reclient && use_siso)`
This CL instead to print a warning message to let users to
know about the deprecation.
`use_siso=false` w/o `use_remoteexec=true` doesn't get this message.

Bug: 379584977, 424659245
Change-Id: Ifda8b86645e6204e3c1f5953d19661ca1a6f42ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7144265
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Junji Watanabe <jwata@google.com>
Auto-Submit: Junji Watanabe <jwata@google.com>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1544222}
NOKEYCHECK=True
GitOrigin-RevId: 1bbce479768123763d46e850360f004e3348ea5a
1 file changed