libretro-build.sh: uname: illegal option -- o

[snigel]

This seems to be before make runs, so I believe it's in the libretro-build script.

snigel@iBookG4 ~/.j/j/l/workspace> ./libretro-build.sh 3dengine
PLATFORM: osx
ARCHITECTURE: Power Macintosh
TARGET: osx
uname: illegal option -- o
usage: uname [-amnprsv]

[orbea]

uname -o is not portable and another option should be used, but I have no way of testing msys or osx so I'm not sure I can fix this... If someone can test those this line should be changed.

https://github.com/libretro/libretro-super/blob/master/libretro-build.sh#L32

Also see.
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/uname.html