Generating stage2 patches fails with a modified env

RVVM uses a forked `riscv-test-env` tree where `write_tohost` is implemented via printing results to UART and shutting down the machine.

This can be seen here: https://github.com/riscv/riscv-test-env/commit/002df18087a5f7c7d068757329244adde3243e93

This works well for `riscv-tests`, but hangs `riscv-vector-tests` build as soon as Spike is invoked to generate test results for stage 2:

```shell
make[1]: Entering directory '/home/lekkit/stuff/riscv-vector-tests'
LD_LIBRARY_PATH=/lib build/pspike --isa=rv64gcv_zvbb_zvbc_zfh_zvfh_zvkg_zvkned_zvknha_zvksed_zvksh_zvl256b_zve64d_zfh_zfhmin_zvfh out/v256x64machine/bin/stage1/vaadd_vv-0 > out/v256x64machine/patches/stage2/vaadd_vv-0.patch
...
[no progress]
```

Shouldn't test env only be used when building stage2? Or maybe altering `write_tohost` is not supposed to work correctly, but how am I supposed to report test status then?

Start by reproducing the stage2 build command that invokes build/pspike and hangs while writing out/v256x64machine/patches/stage2/*.patch. Read the forked riscv-test-env write_tohost implementation and the stage2 build flow; done means stage2 patch generation completes and test results are reported without the modified environment causing a hang.

Written by the indexing model from the issue text.