Add find compiler-rt libs cmake module for windows (#52)

* Add find compiler-rt libs cmake module for windows

This patch adds find compiler-rt libs function imported from
llvm-project/cmake/modules to testsuite repository. Some tests
require to link compiler-rt builtins library on windows and
this function helps locate the library path from install dir.

Author: omjavaid

CMakeLists.txt

@@ -241,6 +241,8 @@ if(CMAKE_SYSTEM_NAME STREQUAL "AIX")
   endif()
 endif()
 
+include(HandleCompilerRT)
+
 include(TestSuite)
 include(SingleMultiSource)
 # Needs by External/sollve_vv.

cmake/modules/HandleCompilerRT.cmake

@@ -0,0 +1,50 @@
+# Find the path to compiler-rt builtins library for the target compiler
+# and return it in `output_variable`.
+function(find_compiler_rt_library variable)
+  set(clang_command ${CMAKE_CXX_COMPILER})
+
+  set(cmd_prefix "")
+  if(MSVC)
+    set(cmd_prefix "/clang:")
+  endif()
+
+  # If the C++ compiler is Clang, run it with -dumpmachine to find
+  # the target triple
+  set(target "")  
+  if(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
+    execute_process(
+      COMMAND "${clang_command}" ${cmd_prefix}-dumpmachine
+      OUTPUT_VARIABLE target
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      ERROR_QUIET
+    )
+  endif()
+
+  # If target is set and COMPILER_RT_LIBRARY_builtins_${target} 
+  # cache variable is not defined, then set it by invoking Clang for the target triple.
+  if(NOT ${target} STREQUAL "" AND NOT DEFINED COMPILER_RT_LIBRARY_builtins_${target})
+    list(APPEND clang_command "${cmd_prefix}--target=${target}")
+    execute_process(
+      COMMAND ${clang_command} "${cmd_prefix}--rtlib=compiler-rt" "${cmd_prefix}-print-libgcc-file-name"
+      RESULT_VARIABLE had_error
+      OUTPUT_VARIABLE library_file
+    )
+    string(STRIP "${library_file}" library_file)
+    file(TO_CMAKE_PATH "${library_file}" library_file)
+    get_filename_component(basename ${library_file} NAME)
+    if(basename MATCHES ".*clang_rt\.([a-z0-9_\-]+)\.(a|lib)")
+      message(STATUS "Found compiler-rt builtin library: ${basename}")
+      set(COMPILER_RT_LIBRARY_builtins_${target} "${basename}" CACHE INTERNAL
+        "compiler-rt library for ${target}")
+    else()
+      message(STATUS "Failed to find compiler-rt library for ${target}")
+      set(COMPILER_RT_LIBRARY_builtins_${target} "" CACHE INTERNAL
+          "compiler-rt library for ${target}")
+    endif()
+  endif()
+  if(DEFINED COMPILER_RT_LIBRARY_builtins_${target})
+    set(${variable} "${COMPILER_RT_LIBRARY_builtins_${target}}" PARENT_SCOPE)
+  else()
+    set(${variable} "" PARENT_SCOPE)
+  endif()
+endfunction()