png2icns.c:328:25: error: implicit declaration of function 'unlink' [-Wimplicit-function-declaration]
  328 |                         unlink(argv[1]);
      |                         ^~~~~~
--- a/icnsutils/png2icns.c
+++ b/icnsutils/png2icns.c
@@ -24,6 +24,7 @@
 #include <stdint.h>
 
 #include <errno.h>
+#include <unistd.h>
 
 #include <png.h>
 #include <icns.h>

