Fix wrong include for musl libc.

--- launcher/anjuta-launcher.c	2014-10-17 21:35:31.000000000 +0200
+++ launcher/anjuta-launcher.c	2015-09-09 22:09:06.719400546 +0200
@@ -22,7 +22,7 @@
 #endif
 
 #include <sys/types.h>
-#include <sys/unistd.h>
+#include <unistd.h>
 #include <sys/wait.h>
 #include <stdio.h>
 #include <glib.h>