Fix libc++ configuration with -fsanitize-coverage

Summary:
a recent change (r280015) in libc++ configuration broke LibFuzzer bot:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fuzzer/builds/12245

It's not restricted just to that bot; any code that uses the sanitize coverage and configures libc++ hits it.

This CL fixes the issue.

Reviewers: compnerd

Subscribers: aizatsky

Differential Revision: https://reviews.llvm.org/D24116

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@280335 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/Modules/CheckLibcxxAtomic.cmake

@@ -16,6 +16,9 @@ function(check_cxx_atomics varname)
   if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
     set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
   endif()
+  if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES -fsanitize-coverage)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters")
+  endif()
   check_cxx_source_compiles("
 #include <cstdint>
 #include <atomic>

cmake/config-ix.cmake

@@ -27,6 +27,9 @@ if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
   if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
     set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
   endif ()
+  if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES -fsanitize-coverage)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters")
+  endif ()
 endif ()
 
 include(CheckLibcxxAtomic)