updates (all over the place) for CFI with multimodule support.

.gitattributes

tools/ret_shadow_stack/rss_instrument.cpp

tools/selective_cfi/SConscript

tools/selective_cfi/scfi_instr.cpp

tools/selective_cfi/zest_cfi_runtime/SConscript32

tools/selective_cfi/zest_cfi_runtime/SConscript64

tools/selective_cfi/zest_cfi_runtime/SConstruct

tools/selective_cfi/zest_cfi_runtime/zest_dispatch64.s

tools/simple_cdi/scdi_instr.cpp

tools/transforms/Rewrite_Utility.cpp

tools/transforms/Rewrite_Utility.hpp