Use cargo rather make to do the generation from the svd files

[YonasJ]

This means that you can just compile the crate without needing to manually run make.

After this patch build.rs does all the work, cargo still does dependency checking.

just run cargo build and it will do all the work.

[KerryRJ]

I am wondering if this is going to be merged as I am finding that the makefile is not portable across platforms and wondering about getting this updated or should I be looking at possibly migrating this to cmake?

I would like build esp32 to validate the asm!() changes in xtensa-lx/xtensa-lx-rt.