RFR: JDK-8234284: [dmg] Change DMG background image to TIFF

[Andy Herrick]

Fix looks fine to me.

adding build-dev since even this simple a makefile change should be 
reviewed by build-dev

On 12/10/2019 10:24 PM, Alexander Matveev wrote:
> Please review fix [2] for jpackage bug [1].
>
>  - Changed background image for DMG to TIFF format, which can be used 
> to embed 2x image to support HiDPI displays.
>
> Thanks,
> Alexander
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8234284
>
> [2] http://cr.openjdk.java.net/~almatvee/8234284/webrev.00/