MinGW: it does not support "-municode" option.

[carlo-bramini]

Hello,
I tried to build Fluidsynth with aarch64-w64-mingw32 cross compiler but it fails with this error message:

aarch64-w64-mingw32-gcc: error: unrecognized command-line option '-municode'; did you mean '-Wunicode'?

It seems that it does not support -municode option.
This option exists for i386 and x86_64 targets, but it seems to be not recognized by Aarch64.
See also:

https://github.com/Windows-on-ARM-Experiments/gcc-woarm64/blob/5c06fd42eead8e3a631fb914fe6a7b41b53ade3c/gcc/config/i386/mingw-w64.h#L26

https://github.com/Windows-on-ARM-Experiments/gcc-woarm64/blob/5c06fd42eead8e3a631fb914fe6a7b41b53ade3c/gcc/config/i386/mingw-w64.opt#L21

Thank you very much for your time.

EDIT:
you can test this issue very easily, by compiling this tiny test program:

int wmain(int argc, char *argv[])
{
return 0;
}

This program uses wmain(), so GCC must use -municode, otherwise it will always print the above error message.