[CIR] Support running tests in standalone builds

The only change needed was making the dependency on mlir-translate
target optional, as mlir-translate is installed as part of mlir
when building standalone.

Author: mgorny

clang/test/CMakeLists.txt

@@ -89,8 +89,12 @@ if(CLANG_ENABLE_CIR)
   list(APPEND CLANG_TEST_DEPS
     cir-opt
     cir-translate
-    mlir-translate
     )
+  if(NOT CLANG_BUILT_STANDALONE)
+    list(APPEND CLANG_TEST_DEPS
+      mlir-translate
+      )
+  endif()
 endif()
 
 if(CLANG_ENABLE_STATIC_ANALYZER)