bitbake: fetch2/s3: allow to use credentials from environment variables

Previously access to AWS S3 was expected to be preconfigured and
credentials to be stored in ~/.aws/credentials. With this change
one can use Bitbake s3 fetcher without AWS credentials stored
permanently as above, just with them exported as the following
environment variables:
 - AWS_ACCESS_KEY_ID,
 - AWS_SECRET_ACCESS_KEY.
 - AWS_DEFAULT_REGION.

(Bitbake rev: 01825699044c42e87e485e6c64cc1dd9b6f87f48)

Signed-off-by: Adam Romanek <romanek.adam@gmail.com>
Signed-off-by: Damian Wrobel <dwrobel@ertelnet.rybnik.pl>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/fetch2/__init__.py

@@ -834,7 +834,10 @@ def runfetchcmd(cmd, d, quiet=False, cleanup=None, log=None, workdir=None):
                   'SSH_AUTH_SOCK', 'SSH_AGENT_PID',
                   'SOCKS5_USER', 'SOCKS5_PASSWD',
                   'DBUS_SESSION_BUS_ADDRESS',
-                  'P4CONFIG']
+                  'P4CONFIG',
+                  'AWS_ACCESS_KEY_ID',
+                  'AWS_SECRET_ACCESS_KEY',
+                  'AWS_DEFAULT_REGION']
 
     if not cleanup:
         cleanup = []