Now I can extract a build command!

lisp/llvm-lib/llvm-build-command.el

@@ -0,0 +1,48 @@
+;;; llvm-build-command.el ---  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2022 Benson Chu
+
+;; Author: Benson Chu <bensonchu457@gmail.com>
+;; Created: [2022-12-23 12:04]
+
+;; This file is not part of GNU Emacs
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+(require 'llvm-shared)
+
+(defun ll/get-llvm-source-build-command (file)
+  (interactive
+   (list
+    (buffer-file-name (current-buffer))))
+
+  (when (not (string-match-p "llvm-project" file))
+    (user-error "This is not an LLVM file!"))
+
+  (let ((build-dir (lls/get-llvm-build-dir)))
+    (compilation-start (-->
+                        (list
+                         (format "touch %s" file)
+                         (lls/ninja-build-tools
+                          build-dir (list (format "%s^" file)) t))
+                        (string-join it " && "))
+                       nil
+                       `(lambda (_)
+                          ,(format "*build-%s*" (file-name-nondirectory file))))))
+
+(provide 'llvm-build-command)
+;;; llvm-build-command.el ends here