Add :internal_config to boringssl fuzzers.

The main motivation is to make the fuzzers pick up the
BORINGSSL_ALLOW_CXX_RUNTIME define, which (in addition to fixing
-Wextra-semi warnigns) makes the fuzzers use the same setting
we use for regular boringssl.

Making most of the other defines consistent is good too.

One undesired side effect is that the fuzzers now also pick up
BORINGSSL_IMPLEMENTATION but that's incorrecto for boringssl's tests already
and improvements for that are tracked in boringssl:258

Bug: 926235
Change-Id: I21a111f308bccb81e23bbdd96b6ba4e218ffd2d5
Reviewed-on: https://chromium-review.googlesource.com/c/1482566
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634727}

third_party/boringssl/BUILD.gn

@@ -237,6 +237,7 @@ if (build_with_chromium) {
         "src/ssl/test/fuzzer.h",
         "src/ssl/test/fuzzer_tags.h",
       ]
+      additional_configs = [ ":internal_config" ]
       deps = [
         ":boringssl_fuzzer",
       ]
@@ -305,6 +306,7 @@ if (build_with_chromium) {
       "src/ssl/test/fuzzer.h",
       "src/ssl/test/fuzzer_tags.h",
     ]
+    additional_configs = [ ":internal_config" ]
     deps = [
       ":boringssl_fuzzer_no_fuzzer_mode",
     ]
@@ -317,6 +319,7 @@ if (build_with_chromium) {
       "src/ssl/test/fuzzer.h",
       "src/ssl/test/fuzzer_tags.h",
     ]
+    additional_configs = [ ":internal_config" ]
     deps = [
       ":boringssl_fuzzer_no_fuzzer_mode",
     ]