Use ARM instruction encoding if building Skia for ARMv6

Skia uses inline assembly that is incompatible with the Thumb instructions
available in ARMv6 and so cannot be built in Thumb mode. ARMv7 and higher
does provide those instructions in Thumb mode and therefore does not need
to be built in ARM mode.

Author: livecodefraser

libskia/libskia.gyp

@@ -133,6 +133,23 @@
   		],
 	},
 
+	'target_defaults':
+	{
+		'target_conditions':
+		[
+			[
+				'toolset_os == "android" and toolset_arch == "armv6"',
+				{
+					'cflags':
+					[
+						# Skia won't compile to ARMv6 Thumb
+						'-marm',
+					],
+				},
+			],
+		],
+	},
+
 	'targets':
 	[
 		# We define separate targets for each set of optimizations as they need