/usr/include/ is in libsteptalk-dev 0.10.0-6+b3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/GNUstep/
/usr/include/GNUstep/Frameworks/
/usr/include/GNUstep/Frameworks/StepTalk.framework/
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/NSInvocation+additions.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/NSObject+additions.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STActor.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STBundleInfo.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STContext.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STConversation.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STEngine.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STEnvironment.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STEnvironmentDescription.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STExterns.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STFileScript.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STFunctions.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STLanguageManager.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STMethod.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STObjCRuntime.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STObjectReference.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STRemoteConversation.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STScript.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STScriptObject.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STScripting.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STScriptsManager.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STSelector.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/STUndefinedObject.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Versions/0/StepTalk.h
/usr/include/GNUstep/Frameworks/StepTalk.framework/Headers
/usr/include/GNUstep/StepTalk