[analyzer] Command line option to show enabled checker list.

This patch adds a command line option to list the checkers that were enabled
by analyzer-checker and not disabled by -analyzer-disable-checker.

It can be very useful to debug long command lines when it is not immediately
apparent which checkers are turned on and which checkers are turned off.

Differential Revision: https://reviews.llvm.org/D23060

llvm-svn: 278006
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index cfbc40b..9a18a63 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -238,6 +238,7 @@
   }
 
   Opts.ShowCheckerHelp = Args.hasArg(OPT_analyzer_checker_help);
+  Opts.ShowEnabledCheckerList = Args.hasArg(OPT_analyzer_list_enabled_checkers);
   Opts.DisableAllChecks = Args.hasArg(OPT_analyzer_disable_all_checks);
 
   Opts.visualizeExplodedGraphWithGraphViz =