Commit Message:

Currently contrib does not build with GCC because of various false positive compiler warnings turned to errors and a GCC compiler bug.

Let's first start with the bug, in GCC apparently
using -gsplit-dwarf (debug fission) and -fdebug-types-section (used to optimize the size of debug inforamtion), when used together, can result in a linker failure.

Refer to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110885 for the GCC bug report of this issue. When it comes to Envoy, optimized builds with GCC are affected on at least GCC 11 (used by --config=docker-gcc) and GCC 12 (and I'm pretty sure the bug isn't fixed in any newer versions either, though I didn't check each version).

Given that we cannot have both debug fission and a debug types section, we decided to abandon the debug types sections and keep the fission.

That being said, apparently both of those options are unmaintained in GCC which poses a question of long term viability of using those or GCC.

Other changes in this commit disable GCC compiler errors for various warnings that happen when building contrib. I checked those warnings and didn't find any true
positive.

And additionally, for warnings that exists in both Clang and GCC, Clang warnings don't trigger, so Clang also disagrees with GCC here.

Additionally missing-requires warning is new and does not exist in GCC 11, but exists in later versions of GCC, so to avoid breaking on this warning for future versions of GCC I disabled it, but also tell GCC to not complain if it sees a flag related to an unknwon diagnostic.

Additional Description:

This is the last change required to make GCC contrib builds work (you can find more context and discussions in #31807)

Risk Level: Low
Testing: building with --config=gcc and --config=docker-gcc
Docs Changes: N/A
Release Notes: N/A
Platform Specific Features: N/A
Fixes #31807

Request variables

Key	Value
ref	45d84c3
sha	212af3a
pr	37131
base-sha	3bf801c
actor	@krinkinmu
message	[contrib] Disable GCC warnings and broken features...
started	1731544520.156326
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)