Cannot launch Groovy on Windows with MSYS

MSYS (Minimal SYStem) uses UNIX format paths but because the JDK requires DOS format JAVA_HOME must be in DOS format. startGroovy does not amend JAVA_HOME for MSYS (it does for Cygwin) before issuing the exec. THis leads to error messages such as:

exec: /h/users/russel/Progs/OddsByLanguage/Gant/Test/C:\Program Files\Java\jdk1.6.0_06/bin/java: cannot execute: No such file or directory

MSYS does not provide an equivalent oif cygpath, and cygpath cannot be assumed.

Although marked as Minor, this is actually a blocking bug as it is impossible to run Groovy in this context/environment.