[tests] Workaround to build Rust on ARMv7

Today, there are some issues identified in the rust toolchain. This is the recommended workaround from below issues:
Spotifyd/spotifyd#425
rust-lang/rust#62896 (comment)

Author: foxtrotzulu94

rust/Cargo.toml

@@ -3,6 +3,9 @@ name = "rust"
 version = "0.1.0"
 authors = ["Javier E. Fajardo <foxtrotzulu94@gmail.com>"]
 
+[profile.release]
+codegen-units = 1
+
 [dependencies]
 rayon = "1.0"
 rust-crypto = { git = "https://github.com/niluxv/rust-crypto", branch = "stable_0.2" }