Add `8bit-counters` option for fuzzing.

This enables coverage counters[1] when fuzzing.

[1] http://clang.llvm.org/docs/SanitizerCoverage.html#coverage-counters

Change-Id: I33fca02d0406b75ac1f7598f41fe4c2ce43538d1
Reviewed-on: https://boringssl-review.googlesource.com/7274
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index eba67ae..0d7be89 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -99,8 +99,8 @@
   add_definitions(-DBORINGSSL_UNSAFE_FUZZER_MODE)
   set(RUNNER_ARGS "-fuzzer")
 
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fsanitize=address -fsanitize-coverage=edge,indirect-calls")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address -fsanitize-coverage=edge,indirect-calls")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fsanitize=address -fsanitize-coverage=edge,indirect-calls,8bit-counters")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address -fsanitize-coverage=edge,indirect-calls,8bit-counters")
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_C_FLAGS} -fsanitize=address")
   link_directories(.)
 endif()