Fix CMakeLists for clang.

CMakeLists.txt

@@ -19,17 +19,19 @@ set(LIBRARY_OUTPUT_PATH "build")
 # where to put generated binaries
 set(EXECUTABLE_OUTPUT_PATH "build")
 
+find_program(CLANG_EXECUTABLE clang++)
+
 # Function to generate rule to cross compile a source file to an IR module.
 # This should be called with the .cc src file and it will generate a
 # src-file-ir target that can be built.
 # e.g. COMPILE_TO_IR(test.cc) generates the "test-ir" make target.
-set(IR_COMPILE_FLAGS "-emit-llvm" "-O3" "-c" "-I../")
+set(IR_COMPILE_FLAGS "-emit-llvm" "-O3" "-c")
 function(COMPILE_TO_IR SRC_FILE)
   get_filename_component(BASE_NAME ${SRC_FILE} NAME_WE)
-  set(OUTPUT_FILE "${LIBRARY_OUTPUT_PATH}/${BASE_NAME}.ll")
+  set(OUTPUT_FILE "build/${BASE_NAME}.ll")
   add_custom_command(
     OUTPUT ${OUTPUT_FILE}
-    COMMAND ${LLVM_CLANG_EXECUTABLE} ${IR_COMPILE_FLAGS} ${SRC_FILE} -o ${OUTPUT_FILE}
+    COMMAND ${CLANG_EXECUTABLE} ${IR_COMPILE_FLAGS} ${SRC_FILE} -o ${OUTPUT_FILE}
     DEPENDS ${SRC_FILE})
   add_custom_target(${BASE_NAME}-ir ALL DEPENDS ${OUTPUT_FILE})
 endfunction(COMPILE_TO_IR)
@@ -39,8 +41,10 @@ add_library(udfsample SHARED udf-sample.cc)
 add_library(udasample SHARED uda-sample.cc hyperloglog-uda.cc)
 
 # Custom targest to cross compile UDA/UDF to ir
-COMPILE_TO_IR(udf-sample.cc )
-COMPILE_TO_IR(uda-sample.cc )
+if (CLANG_EXECUTABLE)
+  COMPILE_TO_IR(udf-sample.cc )
+  COMPILE_TO_IR(uda-sample.cc )
+endif(CLANG_EXECUTABLE)
 
 # This is an example of how to use the test harness to help develop UDF and UDAs.
 add_executable(udf-sample-test udf-sample-test.cc)