Index: ObsoleteFiles.inc
===================================================================
--- ObsoleteFiles.inc
+++ ObsoleteFiles.inc
@@ -36,6 +36,11 @@
 #   xargs -n1 | sort | uniq -d;
 # done
 
+# 20200323: INTERNALLIB don't install headers anymore
+OLD_FILES+=/usr/include/libelftc.h
+OLD_FILES+=/usr/include/libifconfig.h
+OLD_FILES+=/usr/include/libpmcstat.h
+
 # 20200320: cx and ctau drivers retired
 OLD_FILES+=usr/share/man/man4/ctau.4.gz
 OLD_FILES+=usr/share/man/man4/cx.4.gz
Index: share/mk/bsd.lib.mk
===================================================================
--- share/mk/bsd.lib.mk
+++ share/mk/bsd.lib.mk
@@ -489,8 +489,10 @@
 .include <bsd.nls.mk>
 .include <bsd.confs.mk>
 .include <bsd.files.mk>
+.if !defined(INTERNALLIB)
 .include <bsd.incs.mk>
 .endif
+.endif
 
 LINKOWN?=	${LIBOWN}
 LINKGRP?=	${LIBGRP}