Revert "Relax warnings as errors so we can build on Clang 11 (#90)" (#102)

.travis.yml

@@ -6,7 +6,7 @@ os:
   - linux
   - osx
 compiler: clang
-osx_image: xcode10.2
+osx_image: xcode11.2
 
 addons:
   apt:

cmake/rocksdb_flags.cmake

@@ -143,13 +143,8 @@ option(FAIL_ON_WARNINGS "Treat compile warnings as errors" ON)
 if(FAIL_ON_WARNINGS)
   if(MSVC)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /WX")
-  else()
+  else() # assume GCC
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
-    if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-      if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 11)
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error=shadow -Wno-error=defaulted-function-deleted")
-      endif()
-    endif()
   endif()
 endif()