[mlir] Avoid ASan ODR violation in mlir-src-sharder with LLVM dylib (#181045)
Build mlir-src-sharder via add_llvm_executable instead of add_tablegen
to avoid embedding a second copy of LLVM Support when linking against
libLLVM.so. Fixes ASan ODR violation for DisableABIBreakingChecks
Tested with ASan + LLVM dylib configuration; tool runs without abort.
Fixes #180911