Add -Wno-string-concatenation to test/cctest:cctest_sources

v8/test/cctest/interpreter/test-bytecode-generator.cc contains lots of string arrays with intentional concatenation.

Bug: chromium:1114873
Change-Id: Ie9d35c3849b5b0a6d1d01b6ce21fb80a320d8736
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2366829
Commit-Queue: Arthur Eubanks <aeubanks@google.com>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69625}

test/cctest/BUILD.gn

@@ -60,6 +60,12 @@ v8_header_set("cctest_headers") {
   sources = [ "cctest.h" ]
 }
 
+config("cctest_sources_config") {
+  if (is_clang) {
+    cflags = [ "-Wno-string-concatenation" ]
+  }
+}
+
 v8_source_set("cctest_sources") {
   testonly = true
 
@@ -401,6 +407,7 @@ v8_source_set("cctest_sources") {
     "../..:external_config",
     "../..:internal_config_base",
     "../..:v8_tracing_config",
+    ":cctest_sources_config",
   ]
 
   public_deps = [