Cygwin
installation, 'cygpath' is always present, and is in the 'PATH'.

   Libtool uses 'cygpath' to convert from Cygwin (Unix-style) file names
and paths to Windows format when the build platform is Cygwin and the
host platform is MinGW.

   When the host platform is Cygwin, but the build platform is MSYS or
some Unix system, libtool also uses 'cygpath' to convert from Windows to
Cygwin format (after first converting from the build platform format to
Windows format; *Note Native MinGW File Name Conversion::, and *note
Unix/Windows File Name Conversion::.)  Because the build platform is not
Cygwin, 'cygpath' is not (and should not be) in the 'PATH'.  Therefore,
in this configuration the environment variable 'LT_CYGPATH' is required.
*Note LT_CYGPATH::.