everywhere: Use correct macro for gcc-specific warnings

Many warnings were disabled for all compilers, even though they are
gcc-specific warnings. Now that clang has -Wunknown-warning-option
enabled, this can cause compilation failures when building with clang
toolchains.

Use TOOLCHAIN_DISABLE_GCC_WARNING for all gcc-specific macros.

https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
https://clang.llvm.org/docs/DiagnosticsReference.html



Fixes: #84138

Signed-off-by: Tom Hughes <tomhughes@chromium.org>