[emscripten] libskia: Modify libskia build rules to improve font support

* Don't compile fontconfig support into Emscripten libskia

* Change default font directory to `/boot/standalone/`, to simplify
  getting user font files into the right place.

Author: peter-b

libskia/libskia.gyp

@@ -554,22 +554,29 @@
 					{
 						'sources!':
 						[
-							'src/ports/SkFontHost_fontconfig.cpp',
 							'src/ports/SkFontHost_FreeType.cpp',
 							'src/ports/SkFontHost_FreeType_common.cpp',
-                                                        'src/fonts/SkFontMgr_fontconfig.cpp',
-							
 							'src/sfnt/SkOTTable_name.cpp',
 							'src/sfnt/SkOTUtils.cpp',
 						],
 					},
 				],
+				[
+					'OS != "android"',
+					{
+						'sources!':
+						[
+							'src/ports/SkFontHost_fontconfig.cpp',
+                                                        'src/fonts/SkFontMgr_fontconfig.cpp',
+						],
+					},
+				],
                                 [
                                         'OS == "emscripten"',
                                         {
                                                 'defines':
                                                 [
-                                                       'SK_FONT_FILE_PREFIX="/boot/fonts/"',
+                                                       'SK_FONT_FILE_PREFIX="/boot/standalone/"',
                                                 ],
 
                                                 'dependencies':