Fix CPU/GPU test coverage (#5355)
* update default gcov
* enable coverage for testing
* Revert "enable coverage for testing"
This reverts commit ae0a424f710a6e8f1eb5eba326f1db65a278cd13.
* Revert "Disable coverage for now (#5321)"
This reverts commit e45cf4041b38d61611b0eb5a082435410d2a720e.
