cmake: Show supported formats in --help output for --profiling-format

Fixes: #20943

Source/cmakemain.cxx

@@ -97,7 +97,9 @@ const char* cmDocumentationOptions[][2] = {
     "Find problems with variable usage in system "
     "files." },
 #  if !defined(CMAKE_BOOTSTRAP)
-  { "--profiling-format=<fmt>", "Output data for profiling CMake scripts." },
+  { "--profiling-format=<fmt>",
+    "Output data for profiling CMake scripts. Supported formats: "
+    "google-trace" },
   { "--profiling-output=<file>",
     "Select an output path for the profiling data enabled through "
     "--profiling-format." },