git: openjdk/mobile: 8244248: boot-jdk.m4 captures the version line using regex

[duke]

Changeset: e05227a2
Author:    Xin Liu <xxinliu at amazon.com>
Committer: Paul Hohensee <phh at openjdk.org>
Date:      2020-05-07 11:13:21 +0000
URL:       https://git.openjdk.java.net/mobile/commit/e05227a2

8244248: boot-jdk.m4 captures the version line using regex

Use awk instead of head

Reviewed-by: ihse, erikj

! make/autoconf/boot-jdk.m4