-Csplit-debuginfo=unpacked is default on nightly

.cargo/config_fast_builds

@@ -10,7 +10,7 @@ rustflags = ["-Clink-arg=-fuse-ld=lld", "-Zshare-generics=y"]
 # NOTE: you must manually install https://github.com/michaeleisel/zld on mac. you can easily do this with the "brew" package manager:
 # `brew install michaeleisel/zld/zld`
 [target.x86_64-apple-darwin]
-rustflags = ["-C", "link-arg=-fuse-ld=/usr/local/bin/zld", "-Zshare-generics=y", "-Csplit-debuginfo=unpacked"]
+rustflags = ["-C", "link-arg=-fuse-ld=/usr/local/bin/zld", "-Zshare-generics=y"]
 
 [target.x86_64-pc-windows-msvc]
 linker = "rust-lld.exe"