Roll gn from 7f10984b62e3 to 12a6f48f3587

https://gn.googlesource.com/gn.git/+log/7f10984b62e3..12a6f48f3587

2025-04-11 dpranke@google.com Add more on how args are processed to "help execution".

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/gn-chromium-autoroll
Please CC dpranke@chromium.org,dpranke@google.com,thakis@chromium.org on the revert to ensure that a human
is aware of the problem.

To file a bug in Chromium: https://bugs.chromium.org/p/chromium/issues/entry

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Tbr: dpranke@chromium.org,thakis@chromium.org
Change-Id: Ib05c19aecea1c84121a6b221049ce30436b34dd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6450396
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Bot-Commit: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1445683}

DEPS

@@ -539,7 +539,7 @@ vars = {
   'libcxx_revision':       '024b5251a7d927941cb93cbb6f811bcb13ec5ba4',
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:7f10984b62e37d22cec85dfe8bbb335cd6f34466',
+  'gn_version': 'git_revision:12a6f48f3587a95ccfcf2c28d9f05e472b30b580',
 
   # ninja CIPD package.
   'ninja_package': 'infra/3pp/tools/ninja/',