[fuzzer] Don't enable tests when the fuzzer isn't built

Should fix:
http://green.lab.llvm.org/green/job/clang-stage2-coverage-R_build/1527

llvm-svn: 312157

compiler-rt/test/CMakeLists.txt

@@ -58,7 +58,10 @@ if(COMPILER_RT_CAN_EXECUTE_TESTS)
     # CFI tests require diagnostic mode, which is implemented in UBSan.
     compiler_rt_test_runtime(ubsan cfi)
     compiler_rt_test_runtime(sanitizer_common)
+
+    if(COMPILER_RT_BUILD_LIBFUZZER)
       compiler_rt_test_runtime(fuzzer)
+    endif()
 
     foreach(sanitizer ${COMPILER_RT_SANITIZERS_TO_BUILD})
       # cfi testing is gated on ubsan