twister: coverage: set gcov working directory

gcovr runs gcov to generate temporary coverage files into the gcov
working directory. The working directory defaults to gcovr's -r
argument.

When running twister with the --coverage-per-instance argument, multiple
gcovr instances may run in parallel. Since they all share the same gcov
working directory, they may interfere with each other, resulting in
errors like this:

	AssertionError: Sanity check failed, output file
	spinlock.h##4167b923a06cc9590c8eef372f016a6d.gcov doesn't exist
	but no error from GCOV detected.

To fix this, specify a separate gcov working directory for every test
through gcovr's --gcov-object-directory option.

Signed-off-by: Marco Widmer <[email protected]>

Author: marcowidmer

scripts/pylib/twister/twisterlib/coverage.py

@@ -414,6 +414,7 @@ def collect_coverage(self, outdir, coverage_file, ztest_file, coveragelog):
         cmd = ["gcovr", "-r", self.base_dir,
                "--gcov-ignore-parse-errors=negative_hits.warn_once_per_file",
                "--gcov-executable", self.gcov_tool,
+               "--gcov-object-directory", outdir,
                "-e", "tests/*"]
         cmd += excludes + self.options + ["--json", "-o", coverage_file, outdir]
         cmd_str = " ".join(cmd)
@@ -427,6 +428,7 @@ def collect_coverage(self, outdir, coverage_file, ztest_file, coveragelog):
 
         cmd = ["gcovr", "-r", self.base_dir] + self.options
         cmd += ["--gcov-executable", self.gcov_tool,
+                "--gcov-object-directory", outdir,
                 "-f", "tests/ztest", "-e", "tests/ztest/test/*",
                 "--json", "-o", ztest_file, outdir]
         cmd_str = " ".join(cmd)