[mlir] Make sure that aggregate shared libraries define all of their symbols.

[stellaraccident]

Summary

We were hitting issues on Linux where this was only being caught at runtime, and different linkers (BFD vs LLD) are differently strict in such situations. Such libraries will also fail to build properly on Windows (but test coverage of that is limited, so it is better to enforce globally).

mlir/cmake/modules/AddMLIR.cmake

function(add_mlir_pdll_library target inputFile ofn)
 
   # Append the includes used for this file to the pdll_compilation_commands
   # file.
   file(APPEND ${CMAKE_BINARY_DIR}/pdll_compile_commands.yml
       "--- !FileInfo:\n"
       "  filepath: \"${LLVM_TARGET_DEFINITIONS_ABSOLUTE}\"\n"
       "  includes: \"${CMAKE_CURRENT_SOURCE_DIR};${tblgen_includes}\"\n"
   )
-  
   add_public_tablegen_target(${target})
 endfunction()
 
 # Declare a dialect in the include directory
 function(add_mlir_dialect dialect dialect_namespace)
   set(LLVM_TARGET_DEFINITIONS ${dialect}.td)
   mlir_tablegen(${dialect}.h.inc -gen-op-decls)
   mlir_tablegen(${dialect}.cpp.inc -gen-op-defs)
add_mlir_library(${name}
     ${ARG_UNPARSED_ARGUMENTS}
     PARTIAL_SOURCES_INTENDED
     EXCLUDE_FROM_LIBMLIR
     LINK_LIBS PRIVATE
     ${_deps}
     ${ARG_PUBLIC_LIBS}
   )
   target_sources(${name} PRIVATE ${_objects})
+
+  # Linux defaults to allowing undefined symbols in shared libraries whereas
+  # many other platforms are more strict. We want these libraries to be
+  # self contained, and we want any undefined symbols to be reported at
+  # library construction time, not at library use, so make Linux strict too.
+  if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    target_link_options(${name} PRIVATE
+      "LINKER:-z,defs"
+    )
+  endif()
+
   # TODO: Should be transitive.
   set_target_properties(${name} PROPERTIES
     MLIR_AGGREGATE_EXCLUDE_LIBS "${_embed_libs}")
   if(MSVC)
     set_property(TARGET ${name} PROPERTY WINDOWS_EXPORT_ALL_SYMBOLS ON)
   endif()
 
   # Debugging generator expressions can be hard. Uncomment the below to emit