WCC

"Wrapper-CC" or "Win-CC"

WCC allows the visual studio compiler and the Intel compiler for windows to be used as if they were unix cc style compilers. The primary purpose of WCC is for use with Msys. WCC takes options like -c, -o, -I, -l, ext, and then calls the native windows compiler with the appropriate options. There are a few other things that go on beyond just translating command line parameters such as being able to search for dll's in a similar manor to .so's on unix. WCC is also open source and freely distributable.

One can of course still call cl.exe for example from inside a msys rxvt shell window. It is also possible to use automake or multiple Makefile targets to support the native windows compilers. However, WCC enables a several nifty abilities.

the use of a familiar command line option behavior
configure scripts inside msys can use visual studio
its easier to make a portable build system that supports both unix, MinGW, and visual studio
your customer's / end users can choose to build your msys + MinGW project with visual studio
you can use msys + Gmake + autoconf as the build system for your visual studio project

Why would you want to use visual studio or the intel compiler if you are all ready using MinGW + msys? Sometimes using these proprietary compilers is the only way to do certain things. There are still ABI issues to be worked out in some situations. Also using these compilers is currently the only way to create 64-bit windows binaries. Its also nice to be able to demonstrate that a problem is not coming from the use of MinGW.