compiler-rt: Simplify cross-compilation. Don't use native-compiled llvm-config.

    Note: AddLLVM.cmake does not expose the LLVM source directory.
    So if you want to run the test suite, you need to either:

    1) set LLVM_MAIN_SRC_DIR explicitly (to find lit.py)
    2) change AddLLVM.cmake to point to an installed 'lit'.
    3) add_subdirectory(compiler-rt/test) from clang instead of compiler-rt.

https://us.codeaurora.org/patches/quic/llvm/50683/compiler-rt-cross-compilation.patch

Upstream-Status: Pending
Signed-off-by: Greg Fitzgerald <gregf@codeaurora.org>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

Author: kraj

compiler-rt/CMakeLists.txt

@@ -107,7 +107,16 @@ if (COMPILER_RT_STANDALONE_BUILD)
   set(CMAKE_CXX_EXTENSIONS NO)
 
   if (NOT LLVM_RUNTIMES_BUILD)
-    load_llvm_config()
+    find_package(LLVM REQUIRED)
+    list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+
+    # Variables that AddLLVM.cmake depends on (included by AddCompilerRT)
+    set(LLVM_TOOLS_BINARY_DIR "${LLVM_INSTALL_PREFIX}/bin")
+    set(LLVM_LIBRARY_DIR "${LLVM_INSTALL_PREFIX}/lib")
+
+    set(LLVM_LIBRARY_OUTPUT_INTDIR
+      ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
+
   endif()
   if (TARGET intrinsics_gen)
     # Loading the llvm config causes this target to be imported so place it