Buck: Start buck command always from project root

After merging Buck's change 2e2550fcf54680ea4d697398d258d5ac3ba2f60c,
it is now required, that `buck` is always executed in the project root
directory.  Adjust invocation of `buck` to satisfy this requirement.

Change-Id: Ic1c79ad105d814ee23842add74c2dc54548aea47

Documentation/gen_licenses.py

@@ -18,6 +18,7 @@
 from __future__ import print_function
 
 from collections import defaultdict, deque
+from os import chdir, path
 import re
 from shutil import copyfileobj
 from subprocess import Popen, PIPE
@@ -27,6 +28,8 @@ MAIN = ['//gerrit-pgm:pgm', '//gerrit-gwtui:ui_module']
 
 def parse_graph():
   graph = defaultdict(list)
+  while not path.isfile('.buckconfig'):
+    chdir('..')
   p = Popen(
     ['buck', 'audit', 'classpath', '--dot'] + MAIN,
     stdout = PIPE)

tools/pack_war.py

@@ -15,7 +15,7 @@
 
 from __future__ import print_function
 from optparse import OptionParser
-from os import makedirs, path, symlink
+from os import getcwd, chdir, makedirs, path, symlink
 from subprocess import check_call
 import sys
 from util import check_output
@@ -33,6 +33,8 @@ jars = set()
 
 def link_jars(libs, directory):
   makedirs(directory)
+  while not path.isfile('.buckconfig'):
+    chdir('..')
   cp = check_output(['buck', 'audit', 'classpath'] + libs)
   for j in cp.strip().splitlines():
     if j not in jars: