[openmp] [cmake] Fix respecting LIBOMP_LLVM_LIT_EXECUTABLE as full path

[mgorny]

Summary

Fix lit search to correctly respect LIBOMP_LLVM_LIT_EXECUTABLE as full program path.

The variable passed to find_program() is created by CMake as a cache variable, and therefore can be directly overriden by the user. Since this was the design of LIBOMP_LLVM_LIT_EXECUTABLE (as can be deduced from the error messages) and there is no other use of LIT_EXECUTABLE, remove the redundant variable and pass LIBOMP_LLVM_LIT_EXECUTABLE directly to find_program().

Furthermore, the previous code did not work since the HINTS argument specifies more search directories rather than expected full path. Quoting the CMake documentation:

3. Search the paths specified by the HINTS option. These should be paths computed by system introspection, such as a hint provided by the location of another item already found. Hard-coded guesses should be specified with the PATHS option.

[Hahnfeld]

LGTM, thanks for finding and fixing this one!

runtime/test/CMakeLists.txt

if(CMAKE_VERSION VERSION_LESS 3.1.20141117)
     set(cmake_3_2_USES_TERMINAL)
   else()
     set(cmake_3_2_USES_TERMINAL USES_TERMINAL)
   endif()
   set(LIBOMP_TEST_COMPILER ${CMAKE_C_COMPILER} CACHE STRING
     "Compiler to use for testing OpenMP library")
   set(LIBOMP_TEST_OPENMP_FLAG -fopenmp CACHE STRING
     "OpenMP compiler flag to use for testing OpenMP library")
-  set(LIBOMP_LLVM_LIT_EXECUTABLE "" CACHE STRING
-    "Path to llvm-lit")
-  find_program(LIT_EXECUTABLE
+  find_program(LIBOMP_LLVM_LIT_EXECUTABLE
     NAMES llvm-lit lit.py
-    HINTS ${LIBOMP_LLVM_LIT_EXECUTABLE}
     PATHS ${OPENMP_LLVM_TOOLS_DIR})
-  if(NOT LIT_EXECUTABLE)
+  if(NOT LIBOMP_LLVM_LIT_EXECUTABLE)
     libomp_say("Cannot find llvm-lit.")
     libomp_say("Please put llvm-lit in your PATH, set LIBOMP_LLVM_LIT_EXECUTABLE to its full path or point OPENMP_LLVM_TOOLS_DIR to its directory")
     libomp_warning_say("The check-libomp target will not be available!")
     return()
   endif()
   find_program(FILECHECK_EXECUTABLE
     NAMES FileCheck
     PATHS ${OPENMP_LLVM_TOOLS_DIR})
   if (NOT FILECHECK_EXECUTABLE)
     # set to empty string so that lit can disable dependent tests
     set(FILECHECK_EXECUTABLE "")
   endif()
   # Set lit arguments
   # The -j 1 lets the actual tests run with the entire machine.
   # We have one test thread that spawns the tests serially.  This allows
   # Each test to use the entire machine.
   set(LIBOMP_LIT_ARGS_DEFAULT "-sv --show-unsupported --show-xfail")
   if(MSVC OR XCODE)
     set(LIBOMP_LIT_ARGS_DEFAULT "${LIBOMP_LIT_ARGS_DEFAULT} --no-progress-bar")
   endif()
   set(LIBOMP_LIT_ARGS "${LIBOMP_LIT_ARGS_DEFAULT}" CACHE STRING
     "Default options for lit")
   separate_arguments(LIBOMP_LIT_ARGS)
   add_custom_target(check-libomp
-    COMMAND ${PYTHON_EXECUTABLE} ${LIT_EXECUTABLE} ${LIBOMP_LIT_ARGS} ${CMAKE_CURRENT_BINARY_DIR}
+    COMMAND ${PYTHON_EXECUTABLE} ${LIBOMP_LLVM_LIT_EXECUTABLE} ${LIBOMP_LIT_ARGS} ${CMAKE_CURRENT_BINARY_DIR}
     DEPENDS omp
     COMMENT "Running libomp tests"
     ${cmake_3_2_USES_TERMINAL}
   )
 else()
   # LLVM source tree build, test just-built clang
   if(NOT MSVC)
     set(LIBOMP_TEST_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang)