git: openjdk/jdk: 8326831: Clarify test harness control variables in make help

[Magnus Ihse Bursie]

Changeset: c6641c7d
Author:    Ludvig Janiuk <lujaniuk at openjdk.org>
Committer: Magnus Ihse Bursie <ihse at openjdk.org>
Date:      2024-03-05 16:24:54 +0000
URL:       https://git.openjdk.org/jdk/commit/c6641c7d2d5fd3e085e39646c9a350eeb83e3c5b

8326831: Clarify test harness control variables in make help

Reviewed-by: erikj, gli, ihse

! make/Global.gmk