Revert the changes that removed support for old gcc, as stable/12 still

Revert the changes that removed support for old gcc, as stable/12 still
uses gcc 4.2.1 for mips, powerpc and sparc64.

Revert "Revert part of r360964"

This reverts commit 2ebf10e7a1ced5d3dc4059d0595743277464d915.

Revert "Remove tests for obsolete compilers in the build system"

This reverts commit a606cb388f975561c37dbabc2fee82c27ef09929.