install.sh: Improve portability

Both coreutils stat and busybox stat support `-c`, but busybox stat does not support `--printf`.

Author: chirsz-ever

install.sh

@@ -187,7 +187,7 @@ else
   HOMEBREW_REPOSITORY="${HOMEBREW_PREFIX}/Homebrew"
   HOMEBREW_CACHE="${HOME}/.cache/Homebrew"
 
-  STAT_PRINTF=("/usr/bin/stat" "--printf")
+  STAT_PRINTF=("/usr/bin/stat" "-c")
   PERMISSION_FORMAT="%a"
   CHOWN=("/bin/chown")
   CHGRP=("/bin/chgrp")