pkg/codesearch: add skeleton for code searching tool

Add a clang tool that is used for code indexing (tools/clang/codesearch/).
It follows conventions and build procedure of the declextract tool.

Add pkg/codesearch package that aggregates the info exposed by the clang tools,
and allows doing simple queries:
 - show source code of an entity (function, struct, etc)
 - show entity comment
 - show all entities defined in a source file

Add tools/syz-codesearch wrapper tool that allows to create index for a kernel build,
and then run code queries on it.

1 files changed, 10 insertions, 0 deletions

diff --git a/pkg/codesearch/testdata/source0.h b/pkg/codesearch/testdata/source0.h
new file mode 100644
index 000000000..339975b2e
--- /dev/null
+++ b/pkg/codesearch/testdata/source0.h
@@ -0,0 +1,10 @@
+// Copyright 2025 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+/*
+ * Comment about the function in header.
+ * Multi-line just in case.
+ */
+void function_with_comment_in_header();
+
+void same_name_in_several_files();