[mlir][sparse] Fixed CMakeLists.txt to correctly install MLIRSparseTensorEnums

[wrengr]

I talked with @vmurali offline and the problems they're encountering are specific to the IREE setup, and don't affect the LLVM/MLIR monorepo. We're currently trying to figure out how to fix things for IREE, but reverting D136217 would cause a lot of issues for a lot of other users (since it breaks the monorepo itself)

[vmurali]

Understood. Let this differential be a place holder till a real solution can be found after which we can update the differential, and then commit.

[wrengr]

Assuming this passes the buildbot, then lgtm. I have some nits but I can handle those in a followup differential.

mlir/lib/Dialect/SparseTensor/IR/CMakeLists.txt

 # This conditional is copypasta from `add_mlir_library`.
 if(MSVC_IDE OR XCODE)
   set_source_files_properties(${MLIRSparseTensorEnums_srcs}
     PROPERTIES HEADER_FILE_ONLY ON)
 endif()
 # Older versions of cmake (< 3.19) require INTERFACE libraries to separate
 # the `add_library` and `target_sources` calls.
 add_library(MLIRSparseTensorEnums INTERFACE)
-target_sources(MLIRSparseTensorEnums INTERFACE ${MLIRSparseTensorEnums_srcs})
+target_sources(MLIRSparseTensorEnums INTERFACE
+  $<BUILD_INTERFACE:${MLIRSparseTensorEnums_srcs}>
+  $<INSTALL_INTERFACE:mlir/Dialect/SparseTensor/IR/Enums.h>)
 # The `add_mlir_library_install` is required for other libraries to
 # depend on this one, but the conditional itself and the phony target
 # are copypasta from `add_mlir_library`.  Afaict (wrengr), the version
 # in `add_mlir_library` is to prevent `add_mlir_library_install` from
 # raising additional errors whenever the underlying call to `add_llvm_library`
 # fails.  However, since we are using `add_library` directly, I'm not
 # sure if the conditional is helpful/required here or not.
 if(TARGET MLIRSparseTensorEnums)