All instances of mujoco_test in the code base were followed by
a call to target_link_libraries(<testname> fixture gmock).
As anyhow mujoco_test already was calling target_link_libraries
to some predefined list of targets (mujoco and gtest_main),
this PR adds to the list of default linked targets also fixture
and gmock, to reduce the boilerplate.
Furthermore, to completly remove the need for calling
target_link_libraries after a call to mujoco_test, this PR also
add to the mujoco_test macro the ADDITIONAL_LINK_LIBRARIES
argument, that can be used if a given test needs to link some
additional targets beside the default ones.
To permit to use these new features also for mujoco benchmarks,
this PR adds a MAIN_TARGET parameter to mujoco_test, to select
if gtest_main or another target is used to provide the main
entry point to the test executable.
Also unify warning options across Clang and GCC and fix minor issues that was surfaced by this.
PiperOrigin-RevId: 508619655
Change-Id: I59b777bf2dfea4422485670e2427c7d3f5cf6405
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