fix gcc-11.0 warnings

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index ece03e7..37732e1 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -623,7 +623,7 @@
 		unsigned override_units,
 		int extend);
 
-void xpipe(int filedes[2]) FAST_FUNC;
+void xpipe(int *filedes) FAST_FUNC;
 /* In this form code with pipes is much more readable */
 struct fd_pair { int rd; int wr; };
 #define piped_pair(pair)  pipe(&((pair).rd))