[ESI] ESI runtime relies on CIRCT-defined CMake variables

[mortbopet]

E.g. https://github.com/llvm/circt/blob/20e08c092c67adf20d6b4114d06e45d5d8dc4965/lib/Dialect/ESI/runtime/cosim/CMakeLists.txt#L21-L24

relies on CIRCT_TOOLS_DIR. When ESI Runtime is built out-of-tree, CIRCT_TOOLS_DIR is undefined, resulting in an attempted copy of esi-cosim.py to /esi-cosim.py, which is illegal.

Some possible offending locations:

• https://github.com/llvm/circt/blob/5950674a5f32b31820fc734b0da4aa549a3b9c68/lib/Dialect/ESI/runtime/cosim/MtiPliStub/CMakeLists.txt#L3
• https://github.com/llvm/circt/blob/20e08c092c67adf20d6b4114d06e45d5d8dc4965/lib/Dialect/ESI/runtime/cosim/CMakeLists.txt#L24
• https://github.com/llvm/circt/blob/20e08c092c67adf20d6b4114d06e45d5d8dc4965/lib/Dialect/ESI/runtime/cosim/CMakeLists.txt#L29

[teqdruid]

Huh. I could've sworn that I built this out of tree at some point. I'll fix on top of #7241 .