https://cygwin.com/pipermail/cygwin/2001-November/064457.html
bash-2.05a-1: OSTYPE is empty
bash 21ostypeempty
https://cygwin.com/pipermail/cygwin/2001-November/065527.html
OSTYPE not exported from bash for "M-x compile" in NT emacs
for m
https://www.rpmfind.net/linux/rpm2html/search.php?query=perl(Perl%3A%3AOSType)
RPM resource perl(Perl::OSType)
rpmresourceperlostype