The fix for the following bug:
6923488 4/4 need minor tweaks to HotSpot build for Cygwin
breaks the build.bat batch file when run directly from the
Windows command shell.
The "exit ..." calls should be "exit /b ..." calls so that just
the batch file is exited and not the invoking command shell.
Also, the second "dirname" call in get_msc_ver.sh assumes that
dirname can be found on the default PATH. It needs to be
accessed via TOOL_DIR like the other non-Windows commands.
See attached 6938185-webrev-cr0.tgz for the proposed fix.