[CMake] Fix runtimes build for host Windows (default target)

When building runtimes, the compiler name (e.g. clang, clang-cl) is set based on
`CMAKE_SYSTEM_NAME` passed to `llvm_ExternalProject_Add()` through `CMAKE_ARGS` argument.
This mechanism doesn't work well if the target is Windows host.
`runtime_default_target()`/`builtin_default_target()` doesn't provide a way
to specify `CMAKE_SYSTEM_NAME` and doesn't set it either.

This patch appends variables specified in `RUNTIMES_CMAKE_ARGS`/`BUILTINS_CMAKE_ARGS`
to `CMAKE_ARGS` argument of `llvm_ExternalProject_Add()` in the case of called
from `runtime_default_target()`/`builtin_default_target()` thus in particular
it allows passing CMAKE_SYSTEM_NAME whenever it is required.

Reviewed By: phosek, compnerd, plotfi

Differential Revision: https://reviews.llvm.org/D81877

diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index 824d17e..ea73cec 100644 (file)
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -245,6 +245,7 @@ else() # if this is included from LLVM's CMake
                                         -DCMAKE_ASM_COMPILER_TARGET=${TARGET_TRIPLE}
                                         -DCMAKE_C_COMPILER_WORKS=ON
                                         -DCMAKE_ASM_COMPILER_WORKS=ON
+                                        ${BUILTINS_CMAKE_ARGS}
                              PASSTHROUGH_PREFIXES COMPILER_RT
                              USE_TOOLCHAIN
                              ${EXTRA_ARGS})
@@ -395,6 +396,7 @@ else() # if this is included from LLVM's CMake
                                         -DCMAKE_C_COMPILER_WORKS=ON
                                         -DCMAKE_CXX_COMPILER_WORKS=ON
                                         -DCMAKE_ASM_COMPILER_WORKS=ON
+                                        ${RUNTIMES_CMAKE_ARGS}
                              PASSTHROUGH_PREFIXES LLVM_ENABLE_RUNTIMES
                                                   ${ARG_PREFIXES}
                              EXTRA_TARGETS ${extra_targets}