[test-suite] Test failures with libstdc++ 15

[T0b1-iOS]

When compiling the llvm-test-suite on Fedora 42, there are now test failures introduced because of asserts hit in the STL. Specifically, the following tests fail:

Failed Tests (7):
  test-suite :: MultiSource/Benchmarks/DOE-ProxyApps-C++/CLAMR/CLAMR.test
  test-suite :: MultiSource/Benchmarks/DOE-ProxyApps-C++/PENNANT/PENNANT.test
  test-suite :: MultiSource/Benchmarks/DOE-ProxyApps-C++/miniFE/miniFE.test
  test-suite :: SingleSource/UnitTests/Vectorizer/VPlanNativePath/outer-loop-vect.test
  test-suite :: SingleSource/UnitTests/Vectorizer/any-of.test
  test-suite :: SingleSource/UnitTests/Vectorizer/find-last.test
  test-suite :: SingleSource/UnitTests/matrix-types-spec.test

The Vectorizer tests and matrix-types-spec seem to fail because std::numeric_limits<int32_t>::min() and std::numeric_limits<int32_t>::max() are passed into a uniform_int_distribution<uint64_t> (vice-versa for matrix-types-spec.

For the rest I didn't have time to check yet but they all hit asserts because they access a vector out of bounds.

To reproduce:
I would assume any system with libstdc++/gcc 15 will do. (Edit: On my Arch Linux install with gcc 15 the assertions are not getting hit so maybe one actually needs Fedora 42)

cmake -GNinja -Bllvm-test-suite-build -Ccmake/caches/O0.cmake -DCMAKE_C_COMPILER=clang-20 -DCMAKE_CXX_COMPILER=clang++-20 -DTEST_SUITE_SUBDIRS="MultiSource;SingleSource" -DTEST_SUITE_RUN_BENCHMARKS=true -DTEST_SUITE_COLLECT_CODE_SIZE=false

ninja -C llvm-test-suite-build

lit -v llvm-test-suite-build