clang/cmake: Simplify lit detection for standalone builds

[mgorny]

Hmm, I suppose it makes sense. At least at a first glance I don't see how it could yield different results.

[phosek]

LGTM

[Ericson2314]

LGTM. I also can't see why it would act differently.

clang/CMakeLists.txt

if(LLVM_INCLUDE_TESTS)
 
     # Check prebuilt llvm/utils.
     if(EXISTS ${LLVM_TOOLS_BINARY_DIR}/FileCheck${CMAKE_EXECUTABLE_SUFFIX}
         AND EXISTS ${LLVM_TOOLS_BINARY_DIR}/count${CMAKE_EXECUTABLE_SUFFIX}
         AND EXISTS ${LLVM_TOOLS_BINARY_DIR}/not${CMAKE_EXECUTABLE_SUFFIX})
       set(LLVM_UTILS_PROVIDED ON)
     endif()
 
+    # Seek installed Lit.
+    find_program(LLVM_LIT
+                 NAMES llvm-lit lit.py lit
+                 PATHS "${LLVM_MAIN_SRC_DIR}/utils/lit"
+                 DOC "Path to lit.py")
+
     if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
       # Note: path not really used, except for checking if lit was found
-      set(LLVM_LIT ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
       if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/llvm-lit)
         add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/llvm-lit utils/llvm-lit)
       endif()
       if(NOT LLVM_UTILS_PROVIDED)
         add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/FileCheck utils/FileCheck)
         add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/count utils/count)
         add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/not utils/not)
         set(LLVM_UTILS_PROVIDED ON)
         set(CLANG_TEST_DEPS FileCheck count not)
       endif()
       set(UNITTEST_DIR ${LLVM_MAIN_SRC_DIR}/utils/unittest)
       if(EXISTS ${UNITTEST_DIR}/googletest/include/gtest/gtest.h
           AND NOT EXISTS ${LLVM_LIBRARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}gtest${CMAKE_STATIC_LIBRARY_SUFFIX}
           AND EXISTS ${UNITTEST_DIR}/CMakeLists.txt)
         add_subdirectory(${UNITTEST_DIR} utils/unittest)
       endif()
-    else()
-      # Seek installed Lit.
-      find_program(LLVM_LIT
-                   NAMES llvm-lit lit.py lit
-                   PATHS "${LLVM_MAIN_SRC_DIR}/utils/lit"
-                   DOC "Path to lit.py")
     endif()
 
     if(LLVM_LIT)
       # Define the default arguments to use with 'lit', and an option for the user
       # to override.
       set(LIT_ARGS_DEFAULT "-sv")
       if (MSVC OR XCODE)
         set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")