Enable find-missing-symbols-at-link-time for chromeos builds too.

third_party/libexif/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Linux should use system libexif
 if (!is_linux || is_chromeos) {
 
   # TODO(thestig): Properly support building on Linux.
   config("libexif_config") {
     include_dirs = [ "sources" ]
@@ skipping 39 matching lines @@
       ]
 
       ldflags = [ "/DEF:" + rebase_path("libexif.def") ]
 
       cflags = [
         "/wd4018",  # size/unsigned mismatch
         "/wd4267",  # size_t -> ExifLong truncation on amd64
       ]
 
       # TODO(GYP): Handle /analyze switch, when it will be used in GN.
+    } else if (is_linux) {
+      libs = [ "m" ]
     }
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":libexif_config" ]
   }
 }