Kernel: Reintroduce Credentials.cpp to aarch64 build

Author: https://github.com/Quaker762
Commit: 07649bcb02
Pull-request: https://github.com/SerenityOS/serenity/pull/15661
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/FireFox317
Reviewed-by: https://github.com/gunnarbeutner
Reviewed-by: https://github.com/linusg

Kernel/CMakeLists.txt

@@ -499,6 +499,7 @@ else()
 
         # Files from base Kernel
         CommandLine.cpp
+        Credentials.cpp
         KBufferBuilder.cpp
         KString.cpp
         KSyms.cpp