[libcxx] Add a CI configuration for standalone building in llvm-project/runtimes

Generate the llvm-lit script in runtimes/CmakeFiles.txt unless invoked
from llvm/runtimes.

Differential Revision: https://reviews.llvm.org/D109593

GitOrigin-RevId: 565d45541f860d72b2e2f12001104edd78f5b0c3
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 3436cd8..1ec808e 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -13,6 +13,7 @@
 if(LLVM_ENABLE_RUNTIMES STREQUAL "all" )
   set(LLVM_ENABLE_RUNTIMES ${LLVM_ALL_RUNTIMES})
 endif()
+set(COMMON_CMAKE_ARGS "-DHAVE_LLVM_LIT=ON")
 foreach(proj ${LLVM_ENABLE_RUNTIMES})
   set(proj_dir "${CMAKE_CURRENT_SOURCE_DIR}/../../${proj}")
   if(IS_DIRECTORY ${proj_dir} AND EXISTS ${proj_dir}/CMakeLists.txt)
@@ -87,6 +88,7 @@
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
+                                      ${COMMON_CMAKE_ARGS}
                                       ${BUILTINS_CMAKE_ARGS}
                            PASSTHROUGH_PREFIXES COMPILER_RT
                            USE_TOOLCHAIN
@@ -119,6 +121,7 @@
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
+                                      ${COMMON_CMAKE_ARGS}
                                       ${${target}_extra_args}
                            USE_TOOLCHAIN
                            TARGET_TRIPLE ${target}
@@ -236,6 +239,7 @@
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
+                                      ${COMMON_CMAKE_ARGS}
                                       ${RUNTIMES_CMAKE_ARGS}
                            PASSTHROUGH_PREFIXES LLVM_ENABLE_RUNTIMES
                                                 ${ARG_PREFIXES}
@@ -338,6 +342,7 @@
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                       -DLLVM_RUNTIMES_TARGET=${name}
+                                      ${COMMON_CMAKE_ARGS}
                                       ${${name}_extra_args}
                            EXTRA_TARGETS ${${name}_extra_targets}
                                          ${${name}_test_targets}