[OpenMP] Fix runtimes default build (#149871)
The default build of openmp (`cmake -S <llvm-project>/runtimes
-DLLVM_ENABLE_RUNTIMES=openmp`) current fails with
```
CMake Error at /home/meinersbur/src/llvm/flangrt/_src/cmake/Modules/GetClangResourceDir.cmake:17 (string):
string sub-command REGEX, mode MATCH needs at least 5 arguments total to
command.
Call Stack (most recent call first):
/home/meinersbur/src/llvm/flangrt/_src/openmp/CMakeLists.txt:126 (get_clang_resource_dir)
```
The reason is that because it is not a bootstrapping-build, the clang
resource dir that it intends to write files such as `omp-tools.h` into,
is unavailable. Using the Clang resource dir for writing files is
conceptually broken, as that dir might be located in
`/usr/lib/clang/<version>/`. Writing to it is only intended in
bootstrapping builds where Clang is built alongside openmp.
This patch unifies the identification of being in a bootstrapping built.
The same `LLVM_TREE_AVAILABLE` definition is going to be used in
#137828. No reason for each runtime to define its own.
GitOrigin-RevId: 799f28d7a5f155ae5456c87a511fbd18498f6396
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c206386..ab34851 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -115,7 +115,7 @@
option(OPENMP_ENABLE_LIBOMP_PROFILING "Enable time profiling for libomp." OFF)
# Header install location
-if(${OPENMP_STANDALONE_BUILD})
+if(NOT LLVM_TREE_AVAILABLE)
set(LIBOMP_HEADERS_INSTALL_PATH "${CMAKE_INSTALL_INCLUDEDIR}")
else()
include(GetClangResourceDir)
diff --git a/runtime/src/CMakeLists.txt b/runtime/src/CMakeLists.txt
index 698e185..569061c 100644
--- a/runtime/src/CMakeLists.txt
+++ b/runtime/src/CMakeLists.txt
@@ -11,7 +11,7 @@
include(ExtendPath)
# The generated headers will be placed in clang's resource directory if present.
-if(OPENMP_STANDALONE_BUILD OR NOT LLVM_RUNTIMES_BUILD)
+if(NOT LLVM_TREE_AVAILABLE)
set(LIBOMP_HEADERS_INTDIR ${CMAKE_CURRENT_BINARY_DIR})
else()
set(LIBOMP_HEADERS_INTDIR ${LLVM_BINARY_DIR}/${LIBOMP_HEADERS_INSTALL_PATH})
