I clearly did not mean to do this - i.e. create a 123 file commit.

Ah, ok - initially I chose the wrong base.
We need to be able to add the extra sources when enabling the VIXL DISASSEMBLER but not the SIMULATOR. This doesn't fail unless compiled with ubsan support on clang19.

ping @Sonicadvance1

Still weird that the simulator is required if the disassembler is enabled, but whatever.