Add R8 support

Add support for R8 to optimize apps and java libraries.

Test: m checkbuild
Change-Id: I2afd5d7a84912d3ab613c32c599bd1ebe60562e0

java/config/makevars.go

@@ -55,6 +55,7 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 		ctx.Strict("DX_COMMAND", "${DxCmd} -JXms16M -JXmx2048M")
 		ctx.Strict("USE_D8_DESUGAR", "false")
 	}
+	ctx.Strict("R8_COMPAT_PROGUARD", "${R8Cmd}")
 
 	ctx.Strict("TURBINE", "${TurbineJar}")