i#3544 RV64: Enable the build of the drcov test for RV64

[chenhy0106]

1. Enable the document generation for drcov2lcov options as RISC-V binaries now work.
2. Enable the build of the drcov test linux.eintr for RISC-V. This test can be built and runs correctly on the physical machine. However, due to qemu issues, it cannot be added to the RUNS_ON_QEMU list for RISC-V now.

Issue: #3544

[ksco]

Wait, does these newly opened tests checked by CI? We need to add them to RUNS_IN_QEMU for that, right?

Dismissed outdated review

[chenhy0106]

Wait, does these newly opened tests checked by CI? We need to add them to RUNS_IN_QEMU for that, right?

Only build the eintr test without adding it to RUNS_IN_QEMU. Currently, tests that involve creating threads with clone do not seem to pass under qemu-riscv64.

Testing on the physical machine works fine.