Make setup_sanitizer include optional in CMakeLists.txt

[sjain-stanford]

Fixes #1962 (comment)

Context:
This breaks torch-mlir's CMake build when bumping stablehlo.

The CMake build fails with setup_sanitizers. Probably related to #1959 (cc: @fzakaria , @mlevesquedion ). I see the default for STABLEHLO_ENABLE_SANITIZER being OFF, but this code probably needs to be enclosed in an if-endif:

include(SetupSanitizers)
setup_sanitizers()

Error:

  -- Building StableHLO as an external LLVM project
  -- Building with -fPIC
  CMake Error at /_work/torch-mlir/torch-mlir/externals/stablehlo/CMakeLists.txt:147 (include):
    include could not find requested file:
  
      SetupSanitizers
  
  
  CMake Error at /_work/torch-mlir/torch-mlir/externals/stablehlo/CMakeLists.txt:148 (setup_sanitizers):
    Unknown CMake command "setup_sanitizers".
  
  
  -- Configuring incomplete, errors occurred!

[fzakaria]

I think the change is to fix:

list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")

to not be the PROJECT_SOURCE_DIR but a directory relative to the current file which would work in embedded use case.

[fzakaria]

I will test a change using CMAKE_CURRENT_LIST_DIR so that it propagates.

[sjain-stanford]

@fzakaria using CMAKE_CURRENT_LIST_DIR works too. Just pushed the change. Do you want me to still keep the if-endif (I've removed for now)?

[fzakaria]

LGTM thanks!

[fzakaria]

LGTM -- thank you for iterating a little on it.
You also confirmed it worked for the embedded case?

I'm new to the team and wasn't aware who is using that embedded case as well.

[sjain-stanford]

You also confirmed it worked for the embedded case?

I've tested it from torch-mlir where stablehlo is an external git submodule. If that's what you're referring here as the embedded case then yes!