add codegen-units=1 to release profile

This fixes some stack overflow issues when running tests with portable-dispatch disabled. Ideally, we were able to fix those instances without requiring codegen-units=1.

Author: Robbepop

Cargo.toml

@@ -61,3 +61,6 @@ codegen-units = 1
 [profile.miri]
 inherits = "dev"
 debug-assertions = false
+
+[profile.release]
+codegen-units = 1