[CMake] Use the correct filename for adding the AST verifier macro flag

Author: akyrtzi

lib/AST/CMakeLists.txt

@@ -136,6 +136,6 @@ else()
   set(swift_ast_verifier_flag " -DSWIFT_DISABLE_AST_VERIFIER=1")
 endif()
 
-set_property(SOURCE Verifier.cpp APPEND_STRING PROPERTY COMPILE_FLAGS
+set_property(SOURCE ASTVerifier.cpp APPEND_STRING PROPERTY COMPILE_FLAGS
   "${swift_ast_verifier_flag}")