combo-layer: runcmd() enhancements

Allow setting the environment. Due to a subprocess quirk, it must
always be set explicitly (reuses the one from the previous call if not
set, instead of falling back to os.environ).

Embedding nul characters will be useful for parsing git output more
reliably; support dumping such output a bit better.

(From OE-Core rev: 0af4fadafce690fc8357196cf7247bd222c08d10)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/combo-layer

@@ -174,7 +174,7 @@ class Configuration(object):
             logger.error("ERROR: patchutils package is missing, please install it (e.g. # apt-get install patchutils)")
             sys.exit(1)
 
-def runcmd(cmd,destdir=None,printerr=True,out=None):
+def runcmd(cmd,destdir=None,printerr=True,out=None,env=None):
     """
         execute command, raise CalledProcessError if fail
         return output if succeed
@@ -186,7 +186,7 @@ def runcmd(cmd,destdir=None,printerr=True,out=None):
     else:
         err = os.tmpfile()
     try:
-        subprocess.check_call(cmd, stdout=out, stderr=err, cwd=destdir, shell=isinstance(cmd, str))
+        subprocess.check_call(cmd, stdout=out, stderr=err, cwd=destdir, shell=isinstance(cmd, str), env=env or os.environ)
     except subprocess.CalledProcessError,e:
         err.seek(0)
         if printerr:
@@ -195,7 +195,7 @@ def runcmd(cmd,destdir=None,printerr=True,out=None):
 
     err.seek(0)
     output = err.read()
-    logger.debug("output: %s" % output )
+    logger.debug("output: %s" % output.replace(chr(0), '\\0'))
     return output
 
 def action_init(conf, args):