Set the working directory

Set the CWD for clang to that of the Atom project, if that is unable to
be determined use the directory of the file itself.

Author: Arcanemagus

lib/main.js

@@ -2,6 +2,7 @@
 
 // eslint-disable-next-line import/extensions, import/no-extraneous-dependencies
 import { CompositeDisposable } from 'atom';
+import { dirname } from 'path';
 
 let helpers = null;
 let clangFlags = null;
@@ -132,9 +133,15 @@ export default {
 
         args.push(filePath);
 
+        let [projectPath] = atom.project.relativizePath(filePath);
+        if (projectPath === null) {
+          projectPath = dirname(filePath);
+        }
+
         const execOpts = {
           stream: 'stderr',
           allowEmptyStderr: true,
+          cwd: projectPath,
         };
 
         const output = await helpers.exec(this.execPath, args, execOpts);