[lto-nix] enable LTO for release builds using Nix

Cargo.nix

@@ -45,7 +45,7 @@ else let
   inherit (rustLib) fetchCratesIo fetchCrateLocal fetchCrateGit fetchCrateAlternativeRegistry expandFeatures decideProfile genDrvsByProfile;
   profilesByName = {
     dev = builtins.fromTOML "lto = \"off\"\n";
-    release = builtins.fromTOML "debug = true\n";
+    release = builtins.fromTOML "codegen-units = 1\nlto = true\nopt-level = \"s\"\nstrip = true\n";
   };
   rootFeatures' = expandFeatures rootFeatures;
   overridableMkRustCrate = f:

Cargo.toml

@@ -131,7 +131,8 @@ aws-sdk-config = "1.13"
 aws-sdk-s3 = "1.14"
 
 [profile.dev]
-lto = "thin"
+#lto = "thin"	# disabled for now, adds 2-4 min to each CI build
+lto = "off"
 
 [profile.release]
 lto = true