fix(emit): a store package's build program inputs are not watched

A store package's build program may declare inputs, and they were listed in
`watch`; its files are fixed by the version its manifest and lock name, so
only an editable package's declared inputs are inputs that can change.
Found by running the command over lsp-mcpp, whose openkal-musl dependency
declares its own mcpp.toml.

Author: speak-agent

src/build/build_database.cppm

@@ -515,7 +515,12 @@ Rendered render(std::span<const Member> members,
             for (auto const& g : sp.sources) watch_glob(sp.root, g);
         }
         for (auto const& g : member.testDiscover) watch_glob(member.testRoot, g);
+        // Only an editable package's build program inputs can change: a store
+        // package's are fixed by the version its manifest and lock name.
+        std::set<std::filesystem::path> editableRoots;
+        for (auto const& sp : ctx.sourcePackages) editableRoots.insert(sp.root.lexically_normal());
         for (auto const& declared : mcpp::build::declared_program_inputs(member.workDir)) {
+            if (!editableRoots.contains(declared.root.lexically_normal())) continue;
             for (auto const& f : declared.files) watch_file(f);
             for (auto const& g : declared.globs) watch_glob(declared.root, g);
         }