[libfuzzer][Windows] Silence linker warning in unittest

Summary:
Silence warning when linking unittest binary by not passing
-lstdc++ to the linker since it is ignored.

Reviewers: morehouse

Reviewed By: morehouse

Subscribers: mgorny

Differential Revision: https://reviews.llvm.org/D53225

llvm-svn: 344480

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

@@ -17,9 +17,7 @@ list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS --driver-mode=g++)
 
 if(APPLE OR CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
   list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -lc++ -lpthread)
-elseif(WIN32)
-  list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -lstdc++)
-else()
+elseif(NOT WIN32)
   list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -lstdc++ -lpthread)
 endif()