C++ Coverage not working with --test_env="LCOV_MERGER=/bin/true"

[Ryang20718]

Description of the bug:

C++ Code coverage doesn't work with this flag set

Which category does this issue belong to?

C++ Rules

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

add a cc_library and a cc_test, use bazel coverage --combined_report=lcov --instrument_test_targets --instrumentation_filter="//" --test_env="LCOV_MERGER=/bin/true"

To see that coverage isn't getting generated

Which operating system are you running Bazel on?

20.04

What is the output of bazel info release?

6.5.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

No response

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

Removing --test_env="LCOV_MERGER=/bin/true" yields coverage results

[comius]

cc @c-mita for triage

[c-mita]

What's the expectation here?

That coverage works when you appear to be overriding the tool it needs to work?