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

[chris.hegarty at oracle.com]

Changeset: 73c3fe1eefd7
Author:    phh
Date:      2020-05-07 11:13 -0700
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/73c3fe1eefd7

8244248: boot-jdk.m4 captures the version line using regex
Summary: Use awk instead of head
Reviewed-by: ihse, erikj
Contributed-by: xxinliu at amazon.com

! make/autoconf/boot-jdk.m4