WIP Chromite supporting "LEGACY" mode, as requested by Anush.

lib/cros_build_lib.py

Index: lib/cros_build_lib.py
diff --git a/lib/cros_build_lib.py b/lib/cros_build_lib.py
index 2e6876060c1dce08b93bfa630402f598e7ba548d..5cfa622e40782500763ad502257e695984a18edc 100644
--- a/lib/cros_build_lib.py
+++ b/lib/cros_build_lib.py
@@ -26,7 +26,8 @@ def GetCallerName():
 
 def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
                exit_code=False, redirect_stdout=False, redirect_stderr=False,
-               cwd=None, input=None, enter_chroot=False, num_retries=0):
+               cwd=None, input=None, enter_chroot=False, num_retries=0,
+               env=None):
   """Runs a shell command.
 
   Arguments:
@@ -43,6 +44,8 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
     enter_chroot: this command should be run from within the chroot.  If set,
       cwd must point to the scripts directory.
     num_retries: the number of retries to perform before dying
+    env: If non-None, should be a mapping for the environment variables of the
+      command.  Useful syntax: env=dict(os.environ.items() + [('VAR', 'val')])
 
   Returns:
     If exit_code is True, returns the return code of the shell command.
@@ -70,7 +73,7 @@ def RunCommand(cmd, print_cmd=True, error_ok=False, error_message=None,
 
   for retry_count in range(num_retries + 1):
     try:
-      proc = subprocess.Popen(cmd, cwd=cwd, stdin=stdin,
+      proc = subprocess.Popen(cmd, cwd=cwd, env=env, stdin=stdin,
                               stdout=stdout, stderr=stderr)
       (output, error) = proc.communicate(input)
       if exit_code and retry_count == num_retries: