Fix GCC 13 Release build test failures (#7364)

[damyanp]

GCC 13 (e.g. 13.3.0 shipped with Ubuntu 24.04) has a known miscompilation bug in -funswitch-loops (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109934) that causes widespread test failures when building DXC at -O3.

Disable -funswitch-loops for GCC 13, and update the CI pipeline from Ubuntu-22.04 to Ubuntu-24.04 (which ships GCC 13 as default), removing the workaround from #7365.

Fixes #7364

[damyanp]

DXC doesn't build correctly with gcc-14 - -fno-tree-vrp avoids that particular failure, but since there doesn't seem to a bug filed against gcc for that the assumption here is that this is running afoul of some UB that we should address. This change at least lets us move to a more recent compiler.

It looks like this reproduces the gcc-14.2 bug:

https://godbolt.org/z/b1MsjMoqq

[tex3d]

DXC doesn't build correctly with gcc-14 - -fno-tree-vrp avoids that particular failure, ...

Given this, should gcc-13 be chosen explicitly, or -fno-tree-vrp added if using gcc-14? Or will gcc-14 never become the default gcc on Ubuntu-24.04?

[damyanp]

DXC doesn't build correctly with gcc-14 - -fno-tree-vrp avoids that particular failure, ...

Given this, should gcc-13 be chosen explicitly, or -fno-tree-vrp added if using gcc-14?

Assuming that it really is this issue (I've not been able to find a bug report that convincingly looks like it covers it) then the bug is present in 14.2 but not in 14.3. I'd rather cross this bridge when/if we come to it than pre-emptively disable optimizations that might be masking UB in our code.

Or will gcc-14 never become the default gcc on Ubuntu-24.04?

I think that this might actually be the case as well. Ubuntu-latest was another option that I avoided because I didn't want major upgrades happening without our involvement.

[tex3d]

LGTM!