hg: jdk/sandbox: WSL2 fixes

[magnus.ihse.bursie at oracle.com]

Changeset: c88ce17104e3
Author:    ihse
Date:      2020-07-02 04:20 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/c88ce17104e3

WSL2 fixes

! make/autoconf/basic_windows.m4
! make/autoconf/help.m4
! make/autoconf/spec.gmk.in