[libunwind][CMake] Remove LIBUNWIND_BUILD_32_BITS which has been an error for 3 years (#110175)

Author: ldionne

libunwind/CMakeLists.txt

@@ -31,11 +31,6 @@ include(CMakeDependentOption)
 include(HandleCompilerRT)
 
 # Define options.
-option(LIBUNWIND_BUILD_32_BITS "Build 32 bit multilib libunwind. This option is not supported anymore when building the runtimes. Please specify a full triple instead." ${LLVM_BUILD_32_BITS})
-if (LIBUNWIND_BUILD_32_BITS)
-  message(FATAL_ERROR "LIBUNWIND_BUILD_32_BITS is not supported anymore when building the runtimes, please specify a full triple instead.")
-endif()
-
 option(LIBUNWIND_ENABLE_CET "Build libunwind with CET enabled." OFF)
 option(LIBUNWIND_ENABLE_GCS "Build libunwind with GCS enabled." OFF)
 option(LIBUNWIND_ENABLE_ASSERTIONS "Enable assertions independent of build mode." ON)