Fix shared mutable default in BaseBuilder.get_config

Previously, get_configused a mutable default argument for `properties` (i.e. `properties: dict[str, str] = {}`), which caused all instances without an explicit `properties` argument to share the same dictionary. This led to unexpected behavior when one instance modified the dictionary, as changes were reflected across all others and some builders got a wrong value for `jobs`.

This commit replaces the default value with `None` and initializes a new dictionary inside the constructor when no value is provided. This ensures each instance has its own independent `properties` dictionary, preventing unintended side effects.

Author: RazvanLiviuVarzaru

configuration/builders/base.py

@@ -107,7 +107,7 @@ def get_config(
         jobs: int,
         next_build: Callable[[Builder, Iterable[BuildRequest]], BuildRequest],
         tags: list[str] = [],
-        properties: dict[str, str] = {},
+        properties: dict[str, str] = None,
     ) -> util.BuilderConfig:
         """
         Generates a BuilderConfig object for the builder, including worker names,
@@ -133,6 +133,8 @@ def get_config(
         """
         # Jobs is mandatory, otherwise builder to worker allocation at runtime cannot be done
         assert jobs >= 1, "Jobs must be greater than or equal to 1"
+        if not properties:
+            properties = {}
         properties["jobs"] = jobs
 
         # Update worker metadata