[libfuzzer] unittest-style main driver.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 741ae414295b59c909c7deedf062ab756fbf0810..37d845df37dff264f4b815e5d58fef54de952730 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -645,6 +645,8 @@ group("gn_only") {
       "//media/cast:udp_proxy",
       "//native_client/src/trusted/debug_stub:gdb_rsp_unittest",
       "//storage/browser:dump_file_system",
+      "//testing/libfuzzer/fuzzers",
+      "//testing/libfuzzer/tests:libfuzzer_tests",
       "//third_party/angle:libANGLE",
       "//third_party/angle:libEGL",
       "//third_party/angle:libGLESv2",
@@ -728,15 +730,6 @@ group("gn_only") {
       "//blimp:blimp_tests",
     ]
   }
-
-  if (use_libfuzzer || use_drfuzz) {
-    # these are needed only for gn to discover build files.
-    deps += [
-      "//testing/libfuzzer:libfuzzer_main",
-      "//testing/libfuzzer/fuzzers:string_to_int_fuzzer",
-      "//testing/libfuzzer/tests:libfuzzer_tests",
-    ]
-  }
 }
 
 group("gn_mojo_targets") {