Remove option incompatible with Debian hardening.

Forwarded: not-needed
Index: gn/build/gen.py
===================================================================
--- gn.orig/build/gen.py
+++ gn/build/gen.py
@@ -525,9 +525,9 @@ def WriteGNNinja(path, platform, host, o
         '-Wno-implicit-fallthrough',
         '-Wno-redundant-move',
         '-Wno-unused-variable',
-        '-Wno-format',             # Use of %llx, which is supported by _UCRT, false positive
         '-Wno-strict-aliasing',    # Dereferencing punned pointer
         '-Wno-cast-function-type', # Casting FARPROC to RegDeleteKeyExPtr
+        '-Wno-error=nonnull',
       ])
 
     elif platform.is_darwin():