Not sure if you're joking. How do you write an OS without these tools that might be compromised? It's the same problem.
We have tons and tons of backups of clean Linux isos, compilers, etc. The idea that we are going to lose the ability to easily have an uncompromised system is a fairy tale told by the people pushing bootstrapable builds.
Break expectations. Bootstrap it through an esoteric-enough system. Write an Uxn emulator in assembly targeting the cushy environment that UEFI has and you've got a system with graphics, a text editor, a spreadsheet editor, an assembler, games, and maybe even more. I have a Z80-powered email appliance that can be loaded with programs from a connected device. Whoever is breaking my trust in trust surely won't have planned for that.