[runtimes] Pass on COMPILER_RT_BUILD_GWP_ASAN option

[DavidSpickett]

Summary

Currently Arm 32 bit fails to build GWP ASAN, which is fine
because you can disable it with an option.

However this was not being passed to the external project
call.

There are probably more options and functions that could
break this way but this is the one I hit building the llvm
release for Arm 32 bit.

Depends on D139536

[DavidSpickett]

There is maybe a cleaner way to handle things like this but my approach at the minute is fixing what I stumble across.

[DavidSpickett]

And the underlying issue is likely the same as https://github.com/llvm/llvm-project/issues/56900 but I am concentrating on other goals at the moment. Seems logical to pass on options in any case.

[phosek]

This is not the right approach, this would override the setting for every target but that's undesirable. The bootstrapping build allows building runtimes for multiple targets, but only some of them might want to set this option. See https://github.com/llvm/llvm-project/blob/ba57d2ad4e9ae39ab824430baece730649758dd5/clang/cmake/caches/Fuchsia-stage2.cmake#L114 for the correct way to set this option.

llvm/runtimes/CMakeLists.txt

llvm_ExternalProject_Add(runtimes-${name}
                            ${CMAKE_CURRENT_SOURCE_DIR}/../../runtimes
                            DEPENDS ${${name}_deps}
                            # Builtins were built separately above
                            CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
                                       -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR}
+                                      -DCOMPILER_RT_BUILD_GWP_ASAN=${COMPILER_RT_BUILD_GWP_ASAN}
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                       -DLLVM_RUNTIMES_TARGET=${name}
                                       ${COMMON_CMAKE_ARGS}
                                       ${${name}_extra_args}
                            EXTRA_TARGETS ${${name}_extra_targets}