[PATCH 4/4] buildman: Use bytes for the environment

[Simon Glass]

At present we sometimes see problems in gitlab where the environment has
0x80 characters or sequences which are not valid UTF-8.

Avoid this by using bytes for the environment, both internal to buildman
and when writing out the 'env' file. Add a test to make sure this works
as expected.

Reported-by: Marek Vasut <marex at denx.de>
Fixes: e5fc79ea718 ("buildman: Write the environment out to an 'env' file")
Signed-off-by: Simon Glass <sjg at chromium.org>
---

 tools/buildman/builderthread.py |  5 ++---
 tools/buildman/func_test.py     | 12 ++++++++++++
 tools/buildman/toolchain.py     | 24 ++++++++++++++++--------
 3 files changed, 30 insertions(+), 11 deletions(-)

Applied to u-boot-dm, thanks!