[MLIR][ExecutionEngine] Introduce shared library (#87067)

This commit introduces a shared library for the MLIR execution engine.
This library is only built when `LLVM_BUILD_LLVM_DYLIB` is set. Having
such a library allows downstream users to depend on the execution engine
without giving up dynamic linkage. This is especially important for CPU
runner-style tools, as they link against large parts of MLIR and LLVM.

It is alternatively possible to modify the `MLIRExecutionEngine` target
when `LLVM_BUILD_LLVM_DYLIB` is set, to avoid duplicated libraries.

Author: Dinistro

mlir/lib/ExecutionEngine/CMakeLists.txt

@@ -97,6 +97,29 @@ add_mlir_library(MLIRExecutionEngine
   MLIRTargetLLVMIRExport
   )
 
+if(LLVM_BUILD_LLVM_DYLIB)
+  # Build a shared library for the execution engine. Some downstream projects
+  # use this library to build their own CPU runners while preserving dynamic
+  # linkage.
+  add_mlir_library(MLIRExecutionEngineShared
+    ExecutionEngine.cpp
+    SHARED
+
+    EXCLUDE_FROM_LIBMLIR
+
+    ADDITIONAL_HEADER_DIRS
+    ${MLIR_MAIN_INCLUDE_DIR}/mlir/ExecutionEngine
+
+    # Ensures that all necessary dependencies are resolved.
+    DEPENDS
+    MLIRExecutionEngine
+
+    LINK_LIBS PUBLIC
+    LLVM
+    MLIR
+    )
+endif()
+
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 add_mlir_library(MLIRJitRunner
   JitRunner.cpp