Fix failure in printing/BUILD.gn when not using a sysroot. Without this change, gn gen fails with "…

printing/cups_config_helper.py

Index: printing/cups_config_helper.py
diff --git a/printing/cups_config_helper.py b/printing/cups_config_helper.py
index 138a688735a1e0c35919357d3cefd6a44fd2e753..48cb33376e359190b940c8ef4bb4731d1ca6260c 100755
--- a/printing/cups_config_helper.py
+++ b/printing/cups_config_helper.py
@@ -22,8 +22,8 @@ import subprocess
 import sys
 
 def usage():
-  print 'usage: %s {--api-version|--cflags|--ldflags|--libs|--libs-for-gn}' % \
-      sys.argv[0]
+  print ('usage: %s {--api-version|--cflags|--ldflags|--libs|--libs-for-gn} '
+         '[sysroot]' % sys.argv[0])
 
 
 def run_cups_config(cups_config, mode):
@@ -63,7 +63,7 @@ def main():
     return 1
 
   mode = sys.argv[1]
-  if len(sys.argv) > 2:
+  if len(sys.argv) > 2 and sys.argv[2]:
     sysroot = sys.argv[2]
     cups_config = os.path.join(sysroot, 'usr', 'bin', 'cups-config')
     if not os.path.exists(cups_config):