Make webrtc_fuzzer_test use //:common_config.

Before this CL, the GN template webrtc_fuzzer_test was using a build
config that was different from the one used by other WebRTC's targets.

We discovered this in [1] where we detected that RTC_DCHECK_IS_ON had
different values across translation units (1 everywhere and 0 in the
one of the .cc file owned by the webrtc_fuzzer_test).

This was because webrtc_fuzzer_test was not including the default
config //:common_config in its "configs".

[1] - https://webrtc-review.googlesource.com/c/src/+/226465

Bug: None
Change-Id: I5635d90281769c23c5d86ebc8cb494da029c2e85
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226540
Reviewed-by: Andrey Logvin <landrey@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34509}

test/fuzzers/BUILD.gn

@@ -42,6 +42,7 @@ rtc_library("fuzz_data_helper") {
 }
 
 set_defaults("webrtc_fuzzer_test") {
+  configs = rtc_add_configs
   absl_deps = []
 }
 
@@ -52,6 +53,7 @@ template("webrtc_fuzzer_test") {
       ":fuzz_data_helper",
       ":webrtc_fuzzer_main",
     ]
+    configs += invoker.configs
 
     # If absl_deps is [], no action is needed. If not [], then it needs to be
     # converted to //third_party/abseil-cpp:absl when build_with_chromium=true