bitbake: save the initial PATH for use when starting a subprocess

It was possible for bitbake-runtime to be run against a semi-installed
python-native resulting in tracebacks with ImportError's.

To prevent this we stash the initial PATH in the BBConfiguration when bitbake
is started and then set this in the env when launching bitbake-runtask through
subprocesses Popen() call.

Signed-off-by: Joshua Lock <josh@linux.intel.com>

bitbake/bin/bitbake

@@ -157,6 +157,7 @@ Default BBFILES are the .bb files in the current directory.""")
 
     configuration = BBConfiguration(options)
     configuration.pkgs_to_build.extend(args[1:])
+    configuration.initial_path = os.environ['PATH']
 
     #server = bb.server.xmlrpc
     server = bb.server.none

bitbake/lib/bb/runqueue.py

@@ -1042,6 +1042,7 @@ class RunQueueExecute:
                     env[comps[0]] = comps[1]
 
             env['BB_TASKHASH'] = self.rqdata.runq_hash[task]
+            env['PATH'] = self.cooker.configuration.initial_path
 
             sys.stdout.flush()
             sys.stderr.flush()