document declare_dependency(object: ...)

docs/markdown/snippets/dep_objects.md

@@ -0,0 +1,5 @@
+## New `declare_dependency(objects: )` argument
+
+A new argument to `declare_dependency` makes it possible to add objects
+directly to executables that use an internal dependency, without going
+for example through `link_whole`.

docs/yaml/functions/declare_dependency.yaml

@@ -71,3 +71,10 @@ kwargs:
     description: |
       the directories to add to the string search path (i.e. `-J` switch for DMD).
       Must be [[@inc]] objects or plain strings.
+
+  objects:
+    type: list[extracted_obj]
+    since: 1.1.0
+    description: |
+      a list of object files, to be linked directly into the targets that use the
+      dependency.

docs/yaml/objects/build_tgt.yaml

@@ -13,8 +13,8 @@ methods:
     source files. This is typically used to take single object files and link
     them to unit tests or to compile some source files with custom flags. To
     use the object file(s) in another build target, use the
-    `objects:` keyword argument to a [[build_target]] or include them in the command
+    `objects:` keyword argument to a [[build_target]] or [[declare_dependency]],
-    line of a [[custom_target]].
+    or include them in the command line of a [[custom_target]].
   varargs:
     name: source
     type: str | file