Build system tweaks

[sgligorijevicTT]

Ticket

Closes #232

What's changed

I made tt-xla pass down the build type to tt-mlir.
I extracted the directives specifying the compilers to use into a script that calls cmake. There was a typo in one of them, and they likely weren't doing anything as they were in the wrong place in the CMakeLists.txt(inspecting the final .so showed mentions of both GCC 9 and Clang 17). This is one of the reasons why hardcoding a compiler in the CMakeLists.txt is considered an anti-pattern. The new configure script is both a correctness and a QoL improvement.
I changed the activate script to set TTMLIR_TOOLCHAIN_DIR to a default value(same one as tt-mlir default) instead of erroring when not set, as a QoL improvement
I added a build convenience script

What hasn't changed

It's still hardcoded to use ccache for tt-mlir irrespective if it's used for tt-xla or not, I ran into build issues when trying to pass down CMAKE_CXX_COMPILER_LAUNCHER to tt-mlir in cases when it isn't set.

Checklist

• New/Existing tests provide coverage for changes

[github-actions]

	Tests	Passed ✅	Skipped ⚠️	Failed
TT-XLA Tests	599 ran	436 passed	163 skipped	0 failed

Test	Result
No test annotations available

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.82%. Comparing base (9ee5247) to head (290851d).

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #246   +/-   ##
=======================================
  Coverage   77.82%   77.82%           
=======================================
  Files          21       21           
  Lines        1028     1028           
=======================================
  Hits          800      800           
  Misses        228      228           

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[sgligorijevicTT]

As it turns out, there are some good reasons not to build tt-mlir in debug alongside tt-xla

1. It makes running tests much slower, a test that took 10-ish seconds now takes ~5min. That will be fixed by Skip op verification in opDebugString tt-mlir#2157
2. The runtime is noisy. Without some sort of filtering, the outputs are close to unusable.

As an alternative, I could add a separate cmake variable to control tt-mlir build type and default it to release, then users that want the extra info can easily set it trough the configure script.