package/gcc: add support for gcc 11

package/gcc: add support for gcc 11

Disable sparc architecture for gcc 11 due to an recent gcc change
that broke uClibc-ng. The change was reverted by the patch
0005-Revert-re-PR-target-92095-internal-error-with-O1-mcp.patch
for gcc 8.4, 9.3 and 10.1 but stop maintaining it for newer gcc
releases.

Rutime tested:
https://gitlab.com/kubu93/buildroot/-/pipelines/318043235

https://gcc.gnu.org/gcc-11/changes.html
https://gcc.gnu.org/gcc-11/porting_to.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>