[gnome-shell] build: Fix check-for-missing for srcdir != builddir

[Florian Müllner <fmuellner src gnome org>]

commit 1c0e0191e0e52ed3d4b5fa6be841759f8f1a163c
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Jun 21 21:55:06 2016 +0200

    build: Fix check-for-missing for srcdir != builddir

 tools/check-for-missing.py |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/tools/check-for-missing.py b/tools/check-for-missing.py
index 6168375..7b12371 100755
--- a/tools/check-for-missing.py
+++ b/tools/check-for-missing.py
@@ -12,12 +12,13 @@ srcdir=sys.argv[1]
 distdir=sys.argv[2]
 excludes=sys.argv[3:]
 
+cwd=os.getcwd()
 os.chdir(srcdir)
 
 status=0
 for f in subprocess.Popen(["git", "ls-files"], stdout=subprocess.PIPE).stdout:
     f = f.decode('utf-8').strip()
-    if (not os.path.exists(os.path.join(distdir, f)) and
+    if (not os.path.exists(os.path.join(cwd, distdir, f)) and
         not any((fnmatch.fnmatch(f, p) for p in excludes))):
         print("File missing from distribution:", f)
         status=1