elogtool: add pytest for elogtool

This CL adds a python test for elogtool.
It tests the basic functionality of elogtool: list, clear and add.
A future CL will include more complex tests.

BUG=b:172210863
TEST=pytest elogtool_test.py

Change-Id: If1241ad070d1c690c84f5ca61c0487ba27c2a287
Signed-off-by: Ricardo Quesada <ricardoq@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57869
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/cbfstool/tests/README.md

@@ -0,0 +1,26 @@
+# CBFSTool tests
+
+To run the tests do `pytest name_of_the_file.py`. E.g:
+
+```shell
+$ pytest elogtool_test.py
+```
+
+## Dependencies
+
+### Pytest
+
+Requires `pytest`. To install it do:
+
+```shell
+$ pip install --user pytest
+```
+
+### Binaries
+
+Make sure that you have compiled the cbfstool binaries before running the test. e.g:
+
+```shell
+$ cd $COREBOOT_SRC/util/cbfstool
+$ make
+```