Fix handling of array arguments in chromite cros_build_lib.

chromite/lib/cros_build_lib.py

Index: chromite/lib/cros_build_lib.py
diff --git a/chromite/lib/cros_build_lib.py b/chromite/lib/cros_build_lib.py
index 1d2860ba93f8c8ae04b9467b8fba2c4e053b7da9..87fa133b75cab27180bd1c575ec2fe655fc78e45 100644
--- a/chromite/lib/cros_build_lib.py
+++ b/chromite/lib/cros_build_lib.py
@@ -78,9 +78,8 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
   cmd_result.cmd = cmd_str
 
   try:
-    proc = subprocess.Popen(cmd_str, cwd=cwd, stdin=stdin,
-                            stdout=stdout, stderr=stderr,
-                            shell=shell)
+    proc = subprocess.Popen(cmd, cwd=cwd, stdin=stdin, stdout=stdout,
+                            stderr=stderr, shell=shell)
     (cmd_result.output, cmd_result.error) = proc.communicate(input)
     if exit_code:
       cmd_result.returncode = proc.returncode