Fix asm1130 unlink declaration

On non-Windows hosts, include `<unistd.h>` to get the `unlink` function
declaration. Fix comes from open-simh PR 523; fixes a build failure
for asm1130 with modern C compilers.

Author: pmetzger

simulators/Ibm1130/utils/asm1130.c

@@ -146,6 +146,9 @@
 #include <setjmp.h>
 #include <time.h>
 #include <ctype.h>
+#ifndef _WIN32
+#include <unistd.h>
+#endif
 #include "util_io.h"
 
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