lang/rust: Update to 1.55.0

• Set codegen-units=1 [1]
• Add hack to skip cargo update on git sources as a step towards solving [2]
• Fix 'capacity overflow' panics on armv* [3]

Changes: https://blog.rust-lang.org/2021-09-09/Rust-1.55.0.html
PR: 258337
PR: 256099 [1]
PR: 256581 [2]
PR: 257419 [3]
Reviewed by: mikael, pkubaj
Exp-run by: antoine
Differential Revision: https://reviews.freebsd.org/D31872
With hat: rust