Report codegen timings for binary crates

[epage]

Problem

Currently --timings doesn't report codegen timings for binary crates.

Proposed Solution

• Emit unused metadata for bin's so codegen timings get reported
• Or waiting for https://github.com/rust-lang/compiler-team/issues/873

Notes

Created from

• #10960
• https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/reporting.20codegen.20timings.20for.20binary.20crates