GCC 11 and Clang 12 CI build added.
GCC 11 and Clang 12 CI build added.

mattgodbolt/seasocks,mattgodbolt/seasocks,mattgodbolt/seasocks,offa/seasocks,mattgodbolt/seasocks,offa/seasocks,offa/seasocks,mattgodbolt/seasocks,offa/seasocks,offa/seasocks,offa/seasocks,mattgodbolt/seasocks