[Chrome OS] Allow building libFuzzer targets for chromeos

Bug: 906214
Change-Id: Ic82a76d816aa7810c95dd3bd0ecc97b4a5f8bd03
Reviewed-on: https://chromium-review.googlesource.com/c/1352814Reviewed-by: Max Moroz <mmoroz@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611726}

BUILD.gn

@@ -722,7 +722,7 @@ group("gn_all") {
     }
   }
 
-  if ((is_linux && !is_chromeos && !is_chromecast) ||
+  if ((is_linux && !is_chromecast) ||
       (is_win && (use_drfuzz || use_libfuzzer)) || (use_libfuzzer && is_mac)) {
     deps += [
       "//testing/libfuzzer/fuzzers",