Stop formating Rvalues to get function names

[FractalFir]

In

rustc_codegen_gcc/src/builder.rs

Line 367 in 75a4fb9

let func_name = format!("{:?}", func_ptr);

, we format an Rvalue to get a function name. This leaks memory.

We also do the same in

rustc_codegen_gcc/src/builder.rs

Line 235 in 75a4fb9

let func_name = format!("{:?}", func_ptr);

.

This is not a big priority(we leak the name of a function each time we call it), but nontheless something I think should be fixed at some point.