6672777: Broken deploy build from jdk fix 6668781 for cygwin windows
Summary: deploy workspace does not set BUILDDIR, uses it, assumes it is jdk/make.
Reviewed-by: xdono
6668781: Openjdk windows cygwin build failure: no rule to make linker_md.obj target
Summary: Use of GNU make vpath breaks on windows with C:/ style fullpaths
Reviewed-by: xdono