Use MacOS deployment target 10.8 as there seems to be a bug on 10.7 and certain versions of Xcode

See https://bugs.chromium.org/p/chromium/issues/detail?id=620127 for more information

build.cake

@@ -544,7 +544,7 @@ Task ("externals-osx")
     .Does (() =>  
 {
     var buildArch = new Action<string, string> ((arch, skiaArch) => {
-        RunGyp ("skia_arch_type='" + skiaArch + "' skia_gpu=1 skia_osx_deployment_target=10.7", "ninja,xcode");
+        RunGyp ("skia_arch_type='" + skiaArch + "' skia_gpu=1 skia_osx_deployment_target=10.8", "ninja,xcode");
         
         XCodeBuild (new XCodeBuildSettings {
             Project = "native-builds/libSkiaSharp_osx/libSkiaSharp.xcodeproj",

native-builds/libSkiaSharp_osx/libSkiaSharp.xcodeproj/project.pbxproj

@@ -1637,7 +1637,7 @@
 					../../skia/include/utils,
 					../../skia/include/config,
 				);
-				MACOSX_DEPLOYMENT_TARGET = 10.7;
+				MACOSX_DEPLOYMENT_TARGET = 10.8;
 				OTHER_CPLUSPLUSFLAGS = (
 					"-std=c++0x",
 					"-stdlib=libc++",
@@ -1664,7 +1664,7 @@
 					../../skia/include/utils,
 					../../skia/include/config,
 				);
-				MACOSX_DEPLOYMENT_TARGET = 10.7;
+				MACOSX_DEPLOYMENT_TARGET = 10.8;
 				OTHER_CPLUSPLUSFLAGS = (
 					"-std=c++0x",
 					"-stdlib=libc++",

samples/Skia.OSX.Demo/Info.plist

@@ -9,7 +9,7 @@
 	<key>CFBundleVersion</key>
 	<string>1.0</string>
 	<key>LSMinimumSystemVersion</key>
-	<string>10.7</string>
+	<string>10.8</string>
 	<key>CFBundleDevelopmentRegion</key>
 	<string>en</string>
 	<key>CFBundleInfoDictionaryVersion</key>

samples/Skia.OSX.GLDemo/Info.plist

@@ -11,7 +11,7 @@
 	<key>CFBundleVersion</key>
 	<string>1.0</string>
 	<key>LSMinimumSystemVersion</key>
-	<string>10.7</string>
+	<string>10.8</string>
 	<key>CFBundleDevelopmentRegion</key>
 	<string>en</string>
 	<key>CFBundleInfoDictionaryVersion</key>