build libexif_fuzzer only on linux

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
 config("libexif_config") {
   include_dirs = [ "sources" ]
   if (is_clang) {
     cflags = [
       "-Wno-enum-conversion",
@@ skipping 66 matching lines @@
       libs = [ "m" ]
     }
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":libexif_config" ]
   }
 }
 
-# used by libfuzzer fuzzers only atm.
-source_set("libexif_fuzzers") {
-  sources = libexif_sources
+if (is_linux) {
+  # used by libfuzzer fuzzers only atm.
+  source_set("libexif_fuzzers") {
+    sources = libexif_sources
 
-  include_dirs = [ "sources" ]
+    include_dirs = [ "sources" ]
 
-  libs = [ "m" ]
+    libs = [ "m" ]
 
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
 
-  public_configs = [ ":libexif_config" ]
+    public_configs = [ ":libexif_config" ]
+  }
 }