If you want a free build environment on Win32, you should try Cygwin ( http://www.cygwin.com
). It is a try to port the Unix API to Win32 so as to make it possible to build Unix applications on Win32 without too much code modification. With this environment, you'll have all the Unix tools you are used to use (bash, gcc, gdb and nearly all the GNU tools in fact). Small glitch: most of the applications compiled with Cygwin must use a special DLL.
Another possibility is MinGW ( http://www.mingw.org
). It is a port of GCC to native Win32. That is to say, all the application compiled with it does not need any special DLL. I don't know what comes included with it, as I never used it.
There are probably dozen other possibilities (such as DJGPP, which is mor targeted to the MS-DOS environment), but those two seem to be the more often cited. Personnaly, I happen to prefer Cygwin, but probably only because I came across it before I heard of MinGW.
As to know if these environments would be able to build K-Meleon, I really have no idea.