libclc: Use echo rather than true for try_compile

When providing a fake compiler, libclc currently uses 'true' which does
not exist on Windows. Use echo instead as the no-op.

reviewer: jvesely
Differential Revision: https://reviews.llvm.org/D77163

Author: fooishbar

libclc/cmake/CMakeTestCLCCompiler.cmake

@@ -24,7 +24,7 @@ if(NOT CMAKE_CLC_COMPILER_WORKS)
   try_compile(CMAKE_CLC_COMPILER_WORKS ${CMAKE_BINARY_DIR}
     ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testCLCCompiler.cl
     # We never generate executable so bypass the link step
-    CMAKE_FLAGS -DCMAKE_CLC_LINK_EXECUTABLE='true'
+    CMAKE_FLAGS -DCMAKE_CLC_LINK_EXECUTABLE='echo'
     OUTPUT_VARIABLE __CMAKE_CLC_COMPILER_OUTPUT)
   # Move result from cache to normal variable.
   set(CMAKE_CLC_COMPILER_WORKS ${CMAKE_CLC_COMPILER_WORKS})

libclc/cmake/CMakeTestLLAsmCompiler.cmake

@@ -24,7 +24,7 @@ if(NOT CMAKE_LLAsm_COMPILER_WORKS)
   try_compile(CMAKE_LLAsm_COMPILER_WORKS ${CMAKE_BINARY_DIR}
     ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testLLAsmCompiler.ll
     # We never generate executable so bypass the link step
-    CMAKE_FLAGS -DCMAKE_LLAsm_LINK_EXECUTABLE='true'
+    CMAKE_FLAGS -DCMAKE_LLAsm_LINK_EXECUTABLE='echo'
     OUTPUT_VARIABLE __CMAKE_LLAsm_COMPILER_OUTPUT)
   # Move result from cache to normal variable.
   set(CMAKE_LLAsm_COMPILER_WORKS ${CMAKE_LLAsm_COMPILER_WORKS})