Ensure libmutton.ini is created with 0600 permissions (on *nix)

core/utilitiesUNIX.go

@@ -0,0 +1,12 @@
+//go:build !windows
+
+package core
+
+import "syscall"
+
+// setUmask sets the file mode creation mask (umask) for the current process.
+// The call to syscall.Umask needs to be embedded in another function to allow
+// compilation on Windows.
+func setUmask(umask int) {
+	syscall.Umask(umask)
+}