Support invocation of daphne from any directory

Currently, `daphne` must be invoked from the repo's root directory `daphne/`. Otherwise the kernel library cannot be found, and the following error occurs:
```
Failed to create MemoryBuffer for: build/src/runtime/local/kernels/libAllKernels.so
Error: No such file or directory
```

We should support invoking `daphne` from any directory. One reason is that it will be easier for users to call `daphne` from the directory where their DaphneDSL scripts reside.

Thanks to @DerSchmidt for pointing out this issue.

Start by tracing how the daphne invocation resolves build/src/runtime/local/kernels/libAllKernels.so when run from the repository root versus another directory. Confirm the behavior with a DaphneDSL script outside the repo root; done means daphne runs from any working directory without the kernel-library error.

Written by the indexing model from the issue text.