Add MGOS_FW_EXTRA_ATTRS, a way to add extra manifest attributes

```yaml
build_var:
  MGOS_FW_EXTRA_ATTRS: x=y a=1 b=true
```

will add extra attributes to manifest:

```json
{
  x: "y",
  a: 1,
  b: true
}
```

Author: rojer

tools/mgos_fw_meta.py

@@ -330,6 +330,21 @@ def cmd_create_manifest(args):
         if k in bi:
             manifest[k] = bi[k]
 
+    for e in args.extra_attr:
+        if not e:
+            continue
+        k, v = e.split('=', 1)
+        if v in ('true', 'false'):
+            v = (v == 'true')
+        elif v == 'null':
+            v = None
+        else:
+            try:
+                v = int(v, 0)
+            except ValueError:
+                pass
+        manifest[k] = v
+
     for p in args.parts:
         name, attrs = p.split(':', 2)
         part = {}
@@ -508,6 +523,7 @@ def cmd_xxd(args):
     cm_cmd.add_argument('--src_dir', default='.')
     cm_cmd.add_argument('--staging_dir')
     cm_cmd.add_argument('--output', '-o')
+    cm_cmd.add_argument('--extra-attr', metavar='extra_attrs', default=[], action='append')
     cm_cmd.add_argument('parts', nargs='+')
     handlers['create_manifest'] = cmd_create_manifest
 

tools/mk/mgos_fw_meta.mk

@@ -9,6 +9,7 @@
 FW_MANIFEST ?= $(FW_STAGING_DIR)/manifest.json
 FW_ZIP ?= $(FW_DIR)/$(APP)-$(APP_PLATFORM)-last.zip
 FW_META_CMD ?= $(MGOS_PATH)/tools/mgos_fw_meta.py
+MGOS_FW_EXTRA_ATTRS ?=
 
 $(FW_ZIP): $(FW_MANIFEST) $(FW_META_CMD)
 	$(vecho) "ZIP    $@"
@@ -24,6 +25,7 @@ $(FW_MANIFEST): $(FW_META_CMD)
 	$(Q) $(FW_META_CMD) create_manifest \
 	  --name=$(APP) --platform=$(APP_PLATFORM) \
 	  --build_info=$(BUILD_INFO_JSON) \
+	  $(addprefix --extra-attr=,$(MGOS_FW_EXTRA_ATTRS)) \
 	  --staging_dir=$(FW_STAGING_DIR) \
 	  --output=$(FW_MANIFEST) \
 	  $(FW_PARTS)