MinGW provides getopt(), don't build our own

src/libCom/osi/os/WIN32/epicsGetopt.c

@@ -1,3 +1,5 @@
+#ifndef _MINGW
+
 /*
  * Copyright (c) 1987, 1993, 1994
  *	The Regents of the University of California.  All rights reserved.
@@ -121,3 +123,5 @@ int getopt(nargc, nargv, ostr)
 	}
 	return (optopt);			/* dump back option letter */
 }
+
+#endif /* !_MINGW */

src/libCom/osi/os/WIN32/epicsGetopt.h

@@ -12,6 +12,12 @@
 #ifndef _EPICS_GETOPT_H
 #define _EPICS_GETOPT_H
 
+#ifdef _MINGW
+
+#include <unistd.h>
+
+#else /* _MINGW */
+
 #include "shareLib.h"
 
 #ifdef __cplusplus
@@ -28,4 +34,6 @@ epicsShareExtern int optind, opterr, optopt;
 }
 #endif
 
+#endif /* _MINGW */
+
 #endif /* _EPICS_GETOPT_H */