how-to-build.rst: 'crcmod' can be installed from Ubuntu, so 'pip' is not needed.

Documentation/how-to-build.rst

@@ -79,6 +79,12 @@ Dependencies
 
         pip3 install --user crc16
 
+or
+
+    .. code-block:: shell-session
+
+        apt install python3-crcmod
+
 or
 
     .. code-block:: shell-session