Musl libc defined `stat64` as a macro, which causes the build to fail
upon compiling os/linux/getmntany.c due to conflicts between the forward
declaration and the implementation.
This commit fixes that by including <sys/stat.h> in "sys/mnttab.h"
directly.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Hiếu Lê <leorize+oss@disroot.org>
Closes#10195