[CMake] Detecting MinGW MSYS or Cygwin unix style file system

[Brandon J. Van Every]

David Cole wrote:

> To me, the very fact that you are targeting Windows indicates that a  
> *default* value of "C:/Program Files" is entirely appropriate.


MSYS is not "Windows."  It is a Unix workalike, with forward slash 
pathnames, its own / root directory structure, Unix tools in abundance, 
etc.  Do not confuse MinGW and MSYS.  MinGW is a compiler, MSYS is an OS 
environment.  Neither requires the other, although they are often used 
together.

> CMake's default value for something should be  appropriate for the 
> majority of its users.


The majority of MSYS users expect /usr/local/.  Hence, MSYS should be 
detected and treated as its own beast, same as Cygwin shell is.  Here's 
the basic difference between Cygwin and MSYS: the latter is better 
licensed and worse packaged.  Hopefully that fault will change in time.

Gotta go fly away and eat a turkey somewhere distant.


Cheers,
Brandon Van Every