https://github.com/termux/termux-packages/issues/15852
Borrowed from https://github.com/gentoo/gentoo/blob/bb2231b459c7feefc083172482cdcbd41fc43f94/media-gfx/aview/files/aview-1.3.0_rc1-clang16.patch

https://bugs.gentoo.org/871249
--- a/flip.c
+++ b/flip.c
@@ -10,4 +10,5 @@
 #include <string.h>
 #include <sys/time.h>
+#include <ctype.h>
 #include <unistd.h>
 #include <aalib.h>
@@ -59,4 +60,5 @@
 static char *graph_mem;
 
+int f_getkey(void);
 
 static void dcd_color_64( char *data ) {