Add build condition not to build in iOS an unused lib (failing to build empty lib in iOS). Unreview…

gyp/tools.gyp

 # GYP file to build various tools.
 #
 # To build on Linux:
 #  ./gyp_skia tools.gyp && make tools
 #
 # Building on other platforms not tested yet.
 #
 {
   'includes': [
     'apptype_console.gypi',
@@ skipping 250 matching lines @@
         '../debugger/SkObjectParser.h',
         '../debugger/SkObjectParser.cpp',
       ],
       'dependencies': [
         'skia_base_libs.gyp:skia_base_libs',
         'effects.gyp:effects',
         'images.gyp:images',
         'tools.gyp:picture_utils',
       ],
     },
-    {
-      'target_name': 'win_dbghelp',
-      'type': 'static_library',
-      'defines': [
-        'SK_CDB_PATH="<(skia_win_debuggers_path)"',
-      ],
-      'sources': [
-        '../tools/win_dbghelp.h',
-        '../tools/win_dbghelp.cpp',
-      ],
-    },
+  ],
+  'conditions': [
+    ['skia_win_debuggers_path and skia_os == "win"',
+      {
+        'targets': [
+          {
+            'target_name': 'win_dbghelp',
+            'type': 'static_library',
+            'defines': [
+              'SK_CDB_PATH="<(skia_win_debuggers_path)"',
+            ],
+            'sources': [
+              '../tools/win_dbghelp.h',
+              '../tools/win_dbghelp.cpp',
+            ],
+          },
+        ],
+      },
+    ],
   ],
 }
 
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 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: