[build] specify lower symbol level for x86/x64 simple chrome

This is to improve link time for x86/x64 board that was not done in
https://chromium-review.googlesource.com/c/1360194

With this CL, link time of chrome for coral reduced from 14.4s to 4.9s

From collected build log, I see 442 chrome builds for x64 targets in
recent 2 days with 13.99s average link time.
Can I improve productivity of those developers by this CL?

Change-Id: I79f4ead0fa955524cfd849d40e7cb0ff4d1aa99f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1506925
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638880}

build/config/compiler/compiler.gni

@@ -211,7 +211,14 @@ if (symbol_level == -1) {
     # Use lower symbol level in Simple Chrome build for faster link time.
     # For Simple Chrome, this should take precedence over is_official_build,
     # turned on by --internal.
-    symbol_level = 1
+    if ((target_cpu == "x64" || target_cpu == "x86") && !is_debug) {
+      # For release x86/x64 build, specify symbol_level=0 for faster link time.
+      # x86/x64 shows backtraces with symbol_level=0 (arm requires
+      # symbol_level=1).
+      symbol_level = 0
+    } else {
+      symbol_level = 1
+    }
   } else if ((!is_nacl && !is_linux && !is_fuchsia) || is_debug ||
              is_official_build || is_chromecast) {
     # Linux builds slower by having symbols as part of the target binary,