Cargo.toml: Use cgu=4

Author: oech3

Cargo.toml

@@ -590,10 +590,11 @@ required-features = ["uudoc"]
 [profile.release]
 lto = true
 panic = "abort"
-codegen-units = 1
+codegen-units = 4 # should be replaced by 1 without regression
 
 [profile.release-fast]
 inherits = "release"
+codegen-units = 1
 
 # A release-like profile that is as small as possible.
 [profile.release-small]