Auto merge of #3262 - nekopsykose:s390x-largefile, r=JohnTitor

s390x-musl: define O_LARGEFILE constant

from https://git.musl-libc.org/cgit/musl/tree/arch/s390x/bits/fcntl.h?id=4b125dd408d54487dc8843b9553502aa0c4167f8#n16

it's a nop as noted in 75ac488, but afaik we should still expose the symbol(?)

src/unix/linux_like/linux/musl/b64/s390x.rs

@@ -145,6 +145,7 @@ pub const ETIMEDOUT: ::c_int = 110;
 pub const O_APPEND: ::c_int = 1024;
 pub const O_CREAT: ::c_int = 64;
 pub const O_EXCL: ::c_int = 128;
+pub const O_LARGEFILE: ::c_int = 0x8000;
 pub const O_NONBLOCK: ::c_int = 2048;
 pub const SA_NOCLDWAIT: ::c_int = 2;
 pub const SA_ONSTACK: ::c_int = 0x08000000;