[libFuzzer] Disable experimental clang coverage support by default.

Summary:
It can be enabled via "-use_clang_coverage=1" flag. Reason for disabling:
libFuzzer resets Clang Counters and makes it impossible to generate coverage
report for a regular fuzz target (i.e. not standalone build).

Reviewers: kcc

Reviewed By: kcc

Subscribers: kcc

Differential Revision: https://reviews.llvm.org/D38604

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@315029 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerDriver.cpp b/FuzzerDriver.cpp
index cc99534..dcf8d50 100644
--- a/FuzzerDriver.cpp
+++ b/FuzzerDriver.cpp
@@ -604,6 +604,7 @@
   Options.PrintCorpusStats = Flags.print_corpus_stats;
   Options.PrintCoverage = Flags.print_coverage;
   Options.DumpCoverage = Flags.dump_coverage;
+  Options.UseClangCoverage = Flags.use_clang_coverage;
   if (Flags.exit_on_src_pos)
     Options.ExitOnSrcPos = Flags.exit_on_src_pos;
   if (Flags.exit_on_item)