rfnoc_modtool: add: Add option to run make-yaml wizard

CHANGELOG

@@ -6,6 +6,10 @@ Change Log for Releases
 * New Features
   - X3x0: Add support for the gps_iface feature. This allows sending arbitrary
     commands to the GPS module.
+  - rfnoc_modtool: Add a new subcommand, `make-yaml`, that generates a block
+    YAML file from some user inputs. When calling `rfnoc_modtool add`  without
+    a valid block YAML file, the tool will now automatically call `make-yaml` to
+    generate a new YAML file.
 * API Changes
   - `uhd::math::gcd` and `uhd::math::lcm` are removed from the public
      headers. Use `std::gcd` and `std::lcm` instead if C++17 is available,

host/python/uhd/rfnoc_utils/modtool_commands/add.yml

@@ -64,8 +64,28 @@ steps:
   - run_if:
       condition: "${ not bool(descriptor) }"
       steps:
-      - exit:
-          msg: "Aborting: No descriptor file found."
+      - input:
+          dst_var: run_wizard
+          prompt: "Block descriptor file ${ descriptor } does not exist. Would you like to run the YAML creation wizard? (y/n)"
+          type: bool
+      - run_if:
+          condition: "${ run_wizard }"
+          steps:
+          - fork:
+              command: make-yaml
+              args:
+                blockname: "${ blockname }"
+                yaml_descriptor: null
+                copyright_holder: null
+                license: null
+          - exit:
+              msg: "⚠    Skipping block generation -- re-run 'rfnoc_modtool add' after editing the block descriptor file."
+              code: 0
+      - run_if:
+          condition: "${ not run_wizard }"
+          steps:
+            - exit:
+                msg: "Block descriptor file ${ descriptor } does not exist. Aborting."
   - log:
       msg: "Parsing block descriptor file ${ descriptor }..."
       symbol: ⚙️