Tests/RunCMake/get_filename_component: Improve failure message formatting

Tests/RunCMake/get_filename_component/KnownComponents.cmake

diff --git a/Tests/RunCMake/get_filename_component/KnownComponents.cmake b/Tests/RunCMake/get_filename_component/KnownComponents.cmake
index c2762ad..34af12e 100644
--- a/Tests/RunCMake/get_filename_component/KnownComponents.cmake
+++ b/Tests/RunCMake/get_filename_component/KnownComponents.cmake
@@ -1,7 +1,7 @@
 # Assertion macro
 macro(check desc actual expect)
   if(NOT "x${actual}" STREQUAL "x${expect}")
-    message(SEND_ERROR "${desc}: got \"${actual}\", not \"${expect}\"")
+    message(SEND_ERROR "${desc}: got\n  \"${actual}\"\nnot\n  \"${expect}\"")
   endif()
 endmacro()