E3-822: Register dependencies for expanded db files

This follows the same pattern as the .d files generated during compilation; the .d files are generated as a side effect of generating the output file, and we then include them all at build-time to register the correct dependencies. See line 634 of driver.makefile.

tests/test_build.py

@@ -273,17 +273,17 @@ def test_updated_template_files(wrapper):
     substitution_file.write_text("file x.template {pattern {x} {y}}")
 
     template_file = wrapper.module_dir / "x.template"
-    template_file.write_text("record(ai, a) {}")
+    template_file.write_text("record(ai, initial) {}")
 
     base_version = wrapper.get_env_var("EPICS_VERSION_NUMBER")
     db_file = wrapper.module_dir / f"O.{base_version}_Common" / "x.db"
 
     rc, *_ = wrapper.run_make("db_internal")
     assert rc == 0
-    assert db_file.read_text() == "record(ai, a) {}"
+    assert db_file.read_text() == "record(ai, initial) {}"
 
-    template_file.write_text("record(ai, b) {}")
+    template_file.write_text("record(ai, updated) {}")
 
     rc, *_ = wrapper.run_make("db_internal")
     assert rc == 0
-    assert db_file.read_text() == "record(ai, b) {}"
+    assert db_file.read_text() == "record(ai, updated) {}"