hg: jdk/sandbox: Move VS dev env handling to be part of sysroot. Fix ugly wsl hack.

[magnus.ihse.bursie at oracle.com]

Changeset: 7aa1b587927b
Author:    ihse
Date:      2020-07-02 18:26 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/7aa1b587927b

Move VS dev env handling to be part of sysroot. Fix ugly wsl hack.

! make/autoconf/basic_windows.m4
! make/autoconf/configure.ac
! make/autoconf/flags.m4
! make/autoconf/toolchain.m4