[objc] Disable metadata token lookup when using the linker. (#303)
[objc] Disable metadata token lookup when using the linker. (#303)

The linker can re-save assemblies that aren't linked, which may change
metadata tokens.

So we need to disable metadata token lookup when linking.

See also https://github.com/mono/Embeddinator-4000/issues/304.
jonathanpeppers/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,mono/Embeddinator-4000,mono/Embeddinator-4000,mono/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,mono/Embeddinator-4000,mono/Embeddinator-4000,mono/Embeddinator-4000,jonathanpeppers/Embeddinator-4000,mono/Embeddinator-4000