create zip archive in temp dir

ok so there are some problems when you're creating the archive but
you're at the root of the project. Namely, the mod package tries to put
the zip inside of itself. So we have to go around that by creating the
zip somewhere else and moving it. This is the first step in that
process.

zip.go

@@ -66,6 +66,7 @@ func zipcmd(args []string) {
 		outputPath = fmt.Sprintf("%s@%s.zip", modbasename(modpath), version)
 	}
 
+	// check that destination is available
 	log_info.Printf("destination: %s", outputPath)
 	switch _, err := os.Stat(outputPath); {
 	case err == nil:
@@ -76,13 +77,24 @@ func zipcmd(args []string) {
 		bail(1, "unable to check for file at %q: %v", outputPath, err)
 	}
 
-	zf, err := os.OpenFile(outputPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644)
+	zf, err := os.CreateTemp("", fmt.Sprintf("modrn_*_%s_%s.zip", modbasename(modpath), version))
 	if err != nil {
-		bail(1, "output file not opened: %v", err)
+		bail(1, "creating zip failed to get a temp file: %v", err)
 	}
+	defer zf.Close()
+
+	fi, err := zf.Stat()
+	if err != nil {
+		// is this even possible?
+		bail(1, "unable to stat resultant tempfile: %v", err)
+	}
+	abspath := filepath.Join(os.TempDir(), fi.Name())
+	log_info.Printf("zipping into temp file at %s", abspath)
 
 	mv := module.Version{Path: modpath, Version: version}
 	if err := zip.CreateFromDir(zf, mv, pkgdir); err != nil {
 		bail(1, "zip not created: %v", err)
 	}
+
+	log_info.Printf("created zip archive at %v", abspath)
 }