I’m trying to compile an extension on Windows using ruby extconf.rb.
However, if I try it in Cygwin or in a command window (with MinGW’s bin
directory in the PATH), it fails and the mkmf.log file shows that the
“cl” executable is being run.
I don’t have a “cl” on my Windows system, so I need gcc to be used.
How do I indicate to mkmf.rb that I’m running under Cygwin or MinGW?