Test: gcc-12.3.1+20240202-0.1

[ASSI]

The native Gcc compilers have been updated to the latest upstream
snapshot version of the gcc-12 branch:

 gcc-12.3.0+20240202

This build incorporates the experimental v4 patch to use the newlib
locale function in libstdc++ so that other locales (aside from "C")
become usable.

Cygwin does not allow multiple versions of the compilers to be installed
concurrently.

For this build, the D compiler has been disabled since it does not
bootstrap due to the missing Phobos runtime on Cygwin.  No testing
beyond the compiler testsuite has been done.

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