Restore build instructions

README.md

@@ -40,5 +40,18 @@ character and glyph coverage. Amiri development might be restarted in the
 future under a different name with less backward-compatibility constraints, but
 nothing concrete is currently planed.
 
+Building
+--------
+
+To build the fonts you need a few Python packages:
+
+    $ python -m venv amiri
+    $ . amiri/bin/activate
+    $ pip install -r requirements.txt
+
+To build the font files run:
+
+    $ make ttf
+
 [1]: https://www.bibalex.org/bulaqpress/en/bulaq.htm "The Bulaq Press"
 [2]: https://openfontlicense.org "The Open Font License"