Overriding target specification options

So, I recently switched my kernel to mainly target the x86_64-unknown-none target, but that uses the PIC code model and the boot loader doesn't support that yet (and I don't think I can initialize the GOT in kmain). I tried to override the option in .cargo/config.toml, but it isn't working:

[build]
rustflags = ["-C", "relocation-model=pie"]

Is Rustc exclusively overriding anything I set with the built-in definition?