main: Add -C parameter

Add -C parameter to allow specifying alternative working
directory.

Ref:
    https://lists.denx.de/pipermail/tbot/2018-November/000063.html

Signed-off-by: Rahix <hws@denx.de>

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## [Unreleased]
+### Added
+- `-C` parameter to allow setting a different working directory
 
 
 ## [0.6.3] - 2018-11-28

tbot/main.py

@@ -28,6 +28,13 @@ def main() -> None:  # noqa: C901
 
     parser.add_argument("testcase", nargs="*", help="testcase that should be run.")
 
+    parser.add_argument(
+        "-C",
+        metavar="WORKDIR",
+        dest="workdir",
+        help="use WORKDIR as working directory instead of the current directory.",
+    )
+
     parser.add_argument("-b", "--board", help="use this board instead of the default.")
 
     parser.add_argument("-l", "--lab", help="use this lab instead of the default.")
@@ -90,6 +97,11 @@ def main() -> None:  # noqa: C901
 
     args = parser.parse_args()
 
+    if args.workdir:
+        import os
+
+        os.chdir(args.workdir)
+
     from tbot import log
 
     # Determine LogFile