fflush(stdout) to print line by line if stdout is not a tty

To reproduce the issue:
	$ slstatus -s | tee

then it would print only when the stdout buffer is full, by block
of multiple lines.

fflush() makes sure the line is printed at every loop iteration

1 files changed, 1 insertions, 0 deletions

diff --git a/slstatus.c b/slstatus.c
index c1cf8ac..5842b3e 100644
--- a/slstatus.c
+++ b/slstatus.c
@@ -98,6 +98,7 @@ main(int argc, char *argv[])
 
 		if (sflag) {
 			printf("%s\n", status);
+			fflush(stdout);
 		} else {
 			XStoreName(dpy, DefaultRootWindow(dpy), status);
 			XSync(dpy, False);