git: openjdk/lanai: 8242185: Lanai: JDK built on macOS 10.15 fails to run on macOS 10.13

[Kevin Rushforth]

Changeset: 5574cca9
Author:    Kevin Rushforth <kcr at openjdk.org>
Date:      2020-04-07 17:10:18 +0000
URL:       https://git.openjdk.java.net/lanai/commit/5574cca9

8242185: Lanai: JDK built on macOS 10.15 fails to run on macOS 10.13

Specify metal version 2.0 when compiling shaders

! make/lib/Awt2dLibraries.gmk