[mlir] Limit Python dependency to Development.Module when possible.

[mikeurbach]

Summary

After CMake 3.18, we are able to limit the scope of the
find_package(Python3 ...) search to just Development.Module. Searching
for Development will fail in manylinux builds, and isn't necessary
since we are not embedding the Python interpreter. For more information, see:
https://pybind11.readthedocs.io/en/stable/compiling.html#findpython-mode

[stellaraccident]

Nice find!! We should propagate this to downstreams (at least a couple of which already require this version of cmake and don't need the conditional).

[mikeurbach]

In D111383#3050098, @stellaraccident wrote:

We should propagate this to downstreams (at least a couple of which already require this version of cmake and don't need the conditional).

I will take care of doing this for CIRCT, and tagged Sean for visibility on Torch MLIR.

[mehdi_amini]

Sorry I had to revert, this broke the build here: https://lab.llvm.org/buildbot/#/builders/61/builds/15842

[mikeurbach]

Thanks Mehdi. I will take a look at that. We also had some issues downstream so I was planning to revert but you beat me to it.

mlir/CMakeLists.txt

 
 set(MLIR_ENABLE_BINDINGS_PYTHON 0 CACHE BOOL
        "Enables building of Python bindings.")
 set(MLIR_BINDINGS_PYTHON_LOCK_VERSION 1 CACHE BOOL
        "Links to specific python libraries, resolving all symbols.")
 
 if(MLIR_ENABLE_BINDINGS_PYTHON)
   include(MLIRDetectPythonEnv)
+  # After CMake 3.18, we are able to limit the scope of the search to just
+  # Development.Module. Searching for Development will fail in manylinux builds,
+  # and isn't necessary since we are not embedding the Python interpreter.
+  # See https://pybind11.readthedocs.io/en/stable/compiling.html#findpython-mode
+  if(${CMAKE_VERSION} VERSION_LESS "3.18.0")
+    set(_python_development_component Development)
+  else()
+    set(_python_development_component Development.Module)
+  endif()
   find_package(Python3 ${LLVM_MINIMUM_PYTHON_VERSION}
-    COMPONENTS Interpreter Development NumPy REQUIRED)
+    COMPONENTS Interpreter ${_python_development_component} NumPy REQUIRED)
   message(STATUS "Found python include dirs: ${Python3_INCLUDE_DIRS}")
   message(STATUS "Found python libraries: ${Python3_LIBRARIES}")
   message(STATUS "Found numpy v${Python3_NumPy_VERSION}: ${Python3_NumPy_INCLUDE_DIRS}")
   mlir_detect_pybind11_install()
   find_package(pybind11 2.6 CONFIG REQUIRED)
   message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIR}")
   message(STATUS "Python prefix = '${PYTHON_MODULE_PREFIX}', "
                  "suffix = '${PYTHON_MODULE_SUFFIX}', "