Update Clang fuzzers to use libFuzzer bundled with the toolchain

[george.karpenkov]

Summary

Same motivation as https://reviews.llvm.org/D37041

[kcc]

LGTM

tools/clang-format/fuzzer/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=fuzzer")
+
 add_clang_executable(clang-format-fuzzer
   EXCLUDE_FROM_ALL
   ClangFormatFuzzer.cpp
   )
 
 target_link_libraries(clang-format-fuzzer
-  ${CLANG_FORMAT_LIB_DEPS}
-  LLVMFuzzer
-  )
+  ${CLANG_FORMAT_LIB_DEPS})

tools/clang-fuzzer/CMakeLists.txt

 if( LLVM_USE_SANITIZE_COVERAGE )
   set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD})
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=fuzzer")
 
   if(CLANG_ENABLE_PROTO_FUZZER)
     # Create protobuf .h and .cc files, and put them in a library for use by
     # clang-proto-fuzzer components.
     find_package(Protobuf REQUIRED)
     add_definitions(-DGOOGLE_PROTOBUF_NO_RTTI)
     include_directories(${PROTOBUF_INCLUDE_DIRS})
     include_directories(${CMAKE_CURRENT_BINARY_DIR})
if(CLANG_ENABLE_PROTO_FUZZER)
 
     # Build the protobuf fuzzer
     add_clang_executable(clang-proto-fuzzer ExampleClangProtoFuzzer.cpp)
     target_link_libraries(clang-proto-fuzzer
       ${ProtobufMutator_LIBRARIES}
       clangCXXProto
       clangHandleCXX
       clangProtoToCXX
-      LLVMFuzzer
       )
   else()
     # Hack to bypass LLVM's cmake sources check and allow multiple libraries and
     # executables from this directory.
     set(LLVM_OPTIONAL_SOURCES ClangFuzzer.cpp ExampleClangProtoFuzzer.cpp)
   endif()
 
   add_clang_subdirectory(handle-cxx)
 
   add_clang_executable(clang-fuzzer
     EXCLUDE_FROM_ALL
     ClangFuzzer.cpp
     )
 
   target_link_libraries(clang-fuzzer
     clangHandleCXX
-    LLVMFuzzer
     )
 endif()