Always link the MLIR python bindings native extension to libMLIR.so

[mehdi_amini]

Summary

The Python bindings now require -DLLVM_BUILD_LLVM_DYLIB=ON to build.
This change is needed to be able to build multiple Python native
extension without having each of them embedding a copy of MLIR, which
would make them incompatible with each other. Instead they should all
link to the same copy of MLIR.

[stellaraccident]

Lgtm. Also see https://reviews.llvm.org/D90824 where I am trying a different approach. It is easy enough to change as we go forward, so let's land this and keep discussing.

mlir/lib/Bindings/Python/CMakeLists.txt

108–113

Maybe just take this out and put it in the target_link_libraries below?

[mehdi_amini]

mlir/lib/Bindings/Python/CMakeLists.txt

108–113

It is all gone in the next revision :)

mlir/lib/Bindings/Python/CMakeLists.txt

+if(NOT LLVM_BUILD_LLVM_DYLIB)
+  message(FATAL_ERROR "Building the MLIR Python bindings require -DLLVM_BUILD_LLVM_DYLIB=ON")
+endif()
+
 ################################################################################
 # Copy python source tree.
 ################################################################################
 
 set(PY_SRC_FILES
   mlir/__init__.py
   mlir/ir.py
   mlir/dialects/__init__.py

 # For static linkage, better code can be generated if the entire project
 # compiles that way, but that is not enforced here. Instead, include a linker
 # script that explicitly hides anything but the PyInit_* symbols, allowing gc
 # to take place.
 # TODO: Add a Windows .def file and figure out the right thing to do on MacOS.
 set_target_properties(
   MLIRBindingsPythonExtension PROPERTIES CXX_VISIBILITY_PRESET "hidden")
 
 set(PYEXT_DEPS)
-if(LLVM_BUILD_LLVM_DYLIB)
-  list(APPEND PYEXT_DEPS
-    # Depend on libMLIR.so first so that deps primarily come from the shared
-    # library.
-    MLIR
-  )
-endif()
-
-# Full static dependencies are also added and will augment what is in the
-# shared lib if needed (or in fully static builds, will result in mondo-built
-# extension).
-list(APPEND PYEXT_DEPS
-  # Depend only on the MLIR C-API.
-  MLIRCAPIIR
-  MLIRCAPIRegistration
-)
 
 target_link_libraries(MLIRBindingsPythonExtension
   PRIVATE
   ${PYEXT_DEPS}
   ${PYEXT_LIBADD}
 )
 
 add_dependencies(MLIRBindingsPythonExtension MLIRBindingsPythonSources)