hg: jdk/sandbox: Now builds java.base on cygwin.

[magnus.ihse.bursie at oracle.com]

Changeset: 1bd39ca00d92
Author:    ihse
Date:      2020-06-11 13:11 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/1bd39ca00d92

Now builds java.base on cygwin.

! make/RunTestsPrebuilt.gmk
! make/autoconf/basic.m4
! make/autoconf/basic_windows.m4
! make/autoconf/spec.gmk.in
! make/common/JavaCompilation.gmk
! make/common/MakeBase.gmk
! make/jdk/src/classes/build/tools/generatecharacter/GenerateCharacter.java
! make/modules/java.base/gensrc/GensrcCharacterData.gmk
! make/modules/java.base/gensrc/GensrcCharsetCoder.gmk
! make/scripts/fixpath.sh