Add support for preferred arch symlinks

Add a symlink_preferred_arch property to binaries to allow compiling the
binary for multiple architectures and then creating a symlink to the
preferred archicture, for example dalvikvm32 and dalvikvm64, with
dalvikvm symlinked to dalvikvm64.

Test: mmma -j art/dalvikvm
Change-Id: Ied15f2be9d52c01006fe8ac207c175b78558eab1

android/config.go

@@ -75,6 +75,7 @@ type config struct {
 	envFrozen bool
 
 	inMake bool
+
 	OncePer
 }
 
@@ -332,6 +333,14 @@ func (c *config) AllowMissingDependencies() bool {
 	return Bool(c.ProductVariables.Allow_missing_dependencies)
 }
 
+func (c *config) DevicePrefer32BitExecutables() bool {
+	return Bool(c.ProductVariables.DevicePrefer32BitExecutables)
+}
+
+func (c *config) HostPrefer32BitExecutables() bool {
+	return Bool(c.ProductVariables.HostPrefer32BitExecutables)
+}
+
 func (c *config) SkipDeviceInstall() bool {
 	return c.EmbeddedInMake() || Bool(c.Mega_device)
 }