Context:
https://github.com/llvm/llvm-project/pull/107103#discussion_r1925834532
This code is brittle, especially when called from a superproject that
adds the `nanobind-*` target in a different source directory:
```cmake
get_property(all_targets DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY BUILDSYSTEM_TARGETS)
```
The changes here do help with my downstream build, but I'm not sure if
using the `MLIR_DISABLE_CONFIGURE_PYTHON_DEV_PACKAGES` option introduced
in https://github.com/llvm/llvm-project/pull/117934 is the right fix
given that the option is currently scoped directly to one location with
a matching name:
7ad8a3da47/mlir/cmake/modules/MLIRDetectPythonEnv.cmake (L4-L5)
Some other solutions to consider:
1. Search through an explicit list of target names using `if (TARGET)`
2. Iterate over _all_ targets in the project, not just the targets in
the current directory, using code like
https://stackoverflow.com/a/62311397
3. Iterate over targets in the directory known to MLIR
(`llvm-project/mlir/python`)
4. Move this `target_compile_options` setup into
`mlir_configure_python_dev_packages` (I started on this, but that runs
into similar issues where the target is defined in a different
directory)
1a8f49fdda