Add ability to force compile as 64 bit.

When trying to build a single 64 bit and 32 bit image, there are
a few executables that are prefer32. When set, this will force all
of those targets to be compiled as 64 bit.

Test: With this option, drmserver/mediaserver are built as 64 bit.
Test: Without this option, drmserver/mediaserver are built as 32 bit.
Change-Id: I1c3dbe229f9b612ff76b857ca7163b14e7dc92c5

android/variable.go

@@ -447,6 +447,8 @@ type productVariables struct {
 	SepolicyFreezeTestExtraPrebuiltDirs []string `json:",omitempty"`
 
 	GenerateAidlNdkPlatformBackend bool `json:",omitempty"`
+
+	IgnorePrefer32OnDevice bool `json:",omitempty"`
 }
 
 func boolPtr(v bool) *bool {