Runtime checks

- Check for presence of WX when running a GUI app
- Ensure current Erlang runtime matches bytecode on Linux

unix/get_zx

@@ -6,8 +6,15 @@
 version=0.12.3
 zx="zx-$version"
 tarball="$zx.tar.gz"
+target="https://zxq9.com/projects/zomp/$tarball"
+
+if command -v wget &> /dev/null
+  then
+    wget -nv "$target"
+  else
+    curl -s "$target" --output "$tarball"
+fi
 
-wget -nv "https://zxq9.com/projects/zomp/$tarball"
 tar -zxf "$tarball"
 cd "$zx"
 chmod +x install