[compiler-rt] Disable LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON on AIX. (#131200)

LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON is not supported on AIX.
Set it to OFF with a WARNING message on AIX.

compiler-rt/cmake/base-config-ix.cmake

@@ -109,7 +109,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" lib)
   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
     "Path where built compiler-rt libraries should be installed.")
-else(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
+else()
   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
     ${COMPILER_RT_OUTPUT_DIR}/lib/${COMPILER_RT_OS_DIR})
   extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "lib/${COMPILER_RT_OS_DIR}")

llvm/CMakeLists.txt

@@ -1200,6 +1200,13 @@ if (UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
 
   # Also set the correct flags for building shared libraries.
   string(APPEND CMAKE_SHARED_LINKER_FLAGS " -shared")
+
+  # Set LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF as AIX doesn't support it
+  if (LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
+    message(WARNING
+    "LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON is not supported on AIX. LLVM_ENABLE_PER_TARGET_RUNTIME_DIR is set to OFF.")
+    set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR OFF CACHE BOOL "" FORCE)
+  endif()
 endif()
 
 # Build with _XOPEN_SOURCE on z/OS.

runtimes/CMakeLists.txt

@@ -223,6 +223,13 @@ endif()
 # This can be used to detect whether we're in the runtimes build.
 set(LLVM_RUNTIMES_BUILD ON)
 
+if (LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND UNIX AND ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+  # Set LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF as AIX doesn't support it
+  message(WARNING
+  "LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON is not supported on AIX. LLVM_ENABLE_PER_TARGET_RUNTIME_DIR is set to OFF.")
+  set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR OFF CACHE BOOL "" FORCE)
+endif()
+
 foreach(entry ${runtimes})
   get_filename_component(projName ${entry} NAME)