Replace ApiStrToNum uses with ApiLevel.

Test: treehugger
Bug: http://b/154667674
Change-Id: I2954bb21c1cfdeb305f25cfb6c8711c930f6ed50
diff --git a/cc/compiler.go b/cc/compiler.go
index f745820..18a2f62 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -354,7 +354,9 @@
 			flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_APEX_NAME__='\""+ctx.apexVariationName()+"\"'")
 		}
 		if ctx.Device() {
-			flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_SDK_VERSION__="+strconv.Itoa(ctx.apexSdkVersion()))
+			flags.Global.CommonFlags = append(flags.Global.CommonFlags,
+				fmt.Sprintf("-D__ANDROID_SDK_VERSION__=%d",
+					ctx.apexSdkVersion().FinalOrFutureInt()))
 		}
 	}