[clang] [llvm] [llvm][clang] Allocate a new stack instead of spawning a new thread to get more stack space (PR #133173)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-gcc-ubuntu` running on `sie-linux-worker3` while building `clang,llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/174/builds/16239

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-unified-tree) failure: build (failure)
...
19.874 [6/3/787] Linking CXX shared library /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/lib/clang/21/lib/x86_64-unknown-linux-gnu/libclang_rt.tsan.so
22.425 [6/2/788] Building CXX object compiler-rt/lib/asan/CMakeFiles/RTAsan_dynamic.x86_64.dir/asan_interceptors.cpp.o
22.653 [6/1/789] Building CXX object compiler-rt/lib/asan/CMakeFiles/RTAsan.x86_64.dir/asan_interceptors.cpp.o
22.682 [4/2/790] Linking CXX static library compiler-rt/lib/asan/tests/libRTAsanTest.x86_64.a
22.683 [4/1/791] Linking CXX static library /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/lib/clang/21/lib/x86_64-unknown-linux-gnu/libclang_rt.asan.a
22.771 [2/2/792] Generating version list for clang_rt.asan-dynamic-x86_64
22.773 [1/2/793] Generating exported symbols for clang_rt.asan-x86_64
22.798 [1/1/794] Building CXX object compiler-rt/lib/asan/CMakeFiles/RTAsan_dynamic_version_script_dummy.x86_64.dir/dummy.cpp.o
22.867 [0/1/795] Linking CXX shared library /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/lib/clang/21/lib/x86_64-unknown-linux-gnu/libclang_rt.asan.so
381.728 [222/34/6918] Building CXX object unittests/Support/CMakeFiles/SupportTests.dir/ProgramStackTest.cpp.o
FAILED: unittests/Support/CMakeFiles/SupportTests.dir/ProgramStackTest.cpp.o 
/opt/ccache/bin/g++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/unittests/Support -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/unittests/Support -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/build/include -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/include -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/third-party/unittest/googletest/include -I/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/third-party/unittest/googlemock/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wno-dangling-else -Wno-variadic-macros -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -std=c++17 -MD -MT unittests/Support/CMakeFiles/SupportTests.dir/ProgramStackTest.cpp.o -MF unittests/Support/CMakeFiles/SupportTests.dir/ProgramStackTest.cpp.o.d -o unittests/Support/CMakeFiles/SupportTests.dir/ProgramStackTest.cpp.o -c /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/unittests/Support/ProgramStackTest.cpp
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/unittests/Support/ProgramStackTest.cpp: In member function ‘virtual void ProgramStackTest_runOnNewStack_Test::TestBody()’:
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/unittests/Support/ProgramStackTest.cpp:33:55: error: call of overloaded ‘runOnNewStack(int, llvm::function_ref<void(int&)>, int&)’ is ambiguous
   33 |   runOnNewStack(0, function_ref<void(int &)>(func2), A);
      |                                                       ^
In file included from /home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/unittests/Support/ProgramStackTest.cpp:9:
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/include/llvm/Support/ProgramStack.h:48:3: note: candidate: ‘R llvm::runOnNewStack(unsigned int, llvm::function_ref<Ret(Params ...)>, Ts&& ...) [with R = void; Ts = {int&}]’
   48 | R runOnNewStack(unsigned StackSize, function_ref<R(Ts...)> Fn, Ts &&...Args) {
      |   ^~~~~~~~~~~~~
/home/buildbot/buildbot-root/llvm-clang-x86_64-gcc-ubuntu/llvm-project/llvm/include/llvm/Support/ProgramStack.h:55:6: note: candidate: ‘void llvm::runOnNewStack(unsigned int, llvm::function_ref<void(Ts ...)>, Ts&& ...) [with Ts = {int&}]’
   55 | void runOnNewStack(unsigned StackSize, function_ref<void(Ts...)> Fn,
      |      ^~~~~~~~~~~~~
399.092 [222/3/6949] Building CXX object unittests/Frontend/CMakeFiles/LLVMFrontendTests.dir/OpenMPIRBuilderTest.cpp.o
408.595 [222/1/6951] Building CXX object unittests/Frontend/CMakeFiles/LLVMFrontendTests.dir/OpenMPDecompositionTest.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/133173