[compiler-rt][fuzzer] Do not link in libc++ in tests and disable exceptions

[phosek]

LGTM

compiler-rt/lib/fuzzer/tests/CMakeLists.txt

if (APPLE)
     list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -isysroot ${DARWIN_osx_SYSROOT})
   endif()
   list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -lpthread)
 endif()
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND
    COMPILER_RT_LIBCXX_PATH AND
    COMPILER_RT_LIBCXXABI_PATH)
-  list(APPEND LIBFUZZER_UNITTEST_CFLAGS -nostdinc++)
+  list(APPEND LIBFUZZER_UNITTEST_CFLAGS -nostdinc++ -fno-exceptions)
+  list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -nostdlib++ -fno-exceptions)
 endif()
 
 if ("-fvisibility=hidden" IN_LIST LIBFUZZER_CFLAGS)
   # Match visibility settings.
   list(APPEND LIBFUZZER_UNITTEST_CFLAGS "-fvisibility=hidden")
 endif()
 
 if(COMPILER_RT_DEFAULT_TARGET_ARCH IN_LIST FUZZER_SUPPORTED_ARCH)