> MinGW has never "supported" the -mno-cygwin option. It has simply 
> tolerated it. The option never did anything useful and at some point 
> it became an error to even supply it. I'm not sure exactly when but 
> some time after 4.4 sounds reasonable to me.

Hi Oscar! Sorry, I just meant to correct this information: "in gcc 4.x it produces an error preventing build". Even if it doesn't do anything useful, still GCC 4.4 does accept that option normally. If MinGW didn't touch anything relevant, then what Cygwin folks said about 4.x [1] clearly did not come to reality.

> No the developer does not confirm that the -mno-cygin option is 
> required for MinGW.

Not for MinGW, but for building Pidgin. I have just checked it, and -mno-cygwin actually is no longer necessary since 2.10.7 [1], but it was at the time of that message. Even though it didn't do anything meaningful, a GCC like 4.6 would cause build to fail.

> Also from what I've seen I would say that the error message that
> the OP shows there comes from Cygwin's gcc not MinGW.

No, you can use either Cygwin or MinGW MSYS as environment, but the compiler must be MinGW [2].

[1] https://hg.pidgin.im/pidgin/main/rev/c959cde2a7bd
[2] https://developer.pidgin.im/wiki/BuildingWinPidgin#Setupyourbuildenvironment