Add USE_D8_DESUGAR option in build/soong

Add an option to use D8's desugar instead of the standalone version.

USE_D8_DESUGAR=true m would trigger DCHECK in dex2oat unless
https://android-review.googlesource.com/c/platform/art/+/562595 is
patched in as well.

Bug: 69329508
Test: m && USE_D8_DESUGAR=false m

Change-Id: I864d88e257a2ba0b7f19aa5cced537301950e963

java/config/makevars.go

@@ -45,8 +45,15 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 	ctx.Strict("JAR_ARGS", "${JarArgsCmd}")
 	ctx.Strict("JAVADOC", "${JavadocCmd}")
 	ctx.Strict("COMMON_JDK_FLAGS", "${CommonJdkFlags}")
-	ctx.Strict("DX", "${DxCmd}")
-	ctx.Strict("DX_COMMAND", "${DxCmd} -JXms16M -JXmx2048M")
+
+	if ctx.Config().IsEnvTrue("USE_D8_DESUGAR") {
+		ctx.Strict("DX", "${D8Cmd}")
+		ctx.Strict("DX_COMMAND", "${D8Cmd} -JXms16M -JXmx2048M")
+	} else {
+		ctx.Strict("DX", "${DxCmd}")
+		ctx.Strict("DX_COMMAND", "${DxCmd} -JXms16M -JXmx2048M")
+	}
+
 	ctx.Strict("TURBINE", "${TurbineJar}")
 
 	if ctx.Config().IsEnvTrue("RUN_ERROR_PRONE") {