PSA: Removing GCC bots from WebRTC’s continuous integration

[mbon...@webrtc.org]

Starting from March 29th, the following two bots will be removed from WebRTC presubmit and postsubmit bots:

• https://ci.chromium.org/p/webrtc/builders/try/linux_compile_gcc_rel 

• https://ci.chromium.org/p/webrtc/builders/ci/Linux64%20Release%20%28GCC%29

This means that WebRTC will support GCC as best effort. Without CI bots we may break GCC compilation, but we will welcome patches to fix GCC related issues. The GCC version currently used on these bots is more than 7 years old so they are already providing low coverage for GCC.

In case of issues compiling with GCC, please file a patch and we will be happy to review and merge them (see https://webrtc.googlesource.com/src/+/refs/heads/master/docs/native-code/development/index.md for instructions about how to contribute to WebRTC).