Based on other install-headers-*, the destination path should be $(DESTDIR)$(prefix)/$(libdir)/pkgconfig, but it is $(DESTDIR)$(datadir)/pkgconfig.
Excerpt from GNUmakefile:
install-headers-vte: vted-$(MAJOR).pc install-headers-gtkd
(cd srcvte; echo $(SOURCES_VTED) | sed -e s,srcvte/,,g | xargs tar cf -) | (cd $(DESTDIR)$(prefix)/include/d/gtkd-$(MAJOR); tar xv)
install -m 644 vted-$(MAJOR).pc $(DESTDIR)$(prefix)/$(libdir)/pkgconfig
install-headers-peas: peasd-$(MAJOR).pc install-headers-gtkd
(cd srcpeas; echo $(SOURCES_PEASD) | sed -e s,srcpeas/,,g | xargs tar cf -) | (cd $(DESTDIR)$(prefix)/include/d/gtkd-$(MAJOR); tar xv)
install -m 644 peasd-$(MAJOR).pc $(DESTDIR)$(datadir)/pkgconfig
Based on other install-headers-*, the destination path should be
$(DESTDIR)$(prefix)/$(libdir)/pkgconfig, but it is$(DESTDIR)$(datadir)/pkgconfig.Excerpt from GNUmakefile: