Define a make variable for merged compat config.

This allows it to be added to the dist target.

Test: m dist
Change-Id: I1d913577f43a2ba3cb134ed35a7c98be76da2bd1

java/platform_compat_config.go

@@ -80,6 +80,12 @@ func (p *platformCompatConfigSingleton) GenerateBuildActions(ctx android.Singlet
 	p.metadata = outputPath
 }
 
+func (p *platformCompatConfigSingleton) MakeVars(ctx android.MakeVarsContext) {
+	if p.metadata != nil {
+		ctx.Strict("INTERNAL_PLATFORM_MERGED_COMPAT_CONFIG", p.metadata.String())
+	}
+}
+
 func (p *platformCompatConfig) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	rule := android.NewRuleBuilder()