I get the following error during build:

...
Making install in doc
make[2]: Entering directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc'
Making install in reference
make[3]: Entering directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc/reference'
make[4]: Entering directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc/reference'
make[4]: Nothing to be done for `install-exec-am'.
installfiles=`echo /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/*`; \
	if test "$installfiles" = '/home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/*'; \
	then echo '-- Nothing to install' ; \
	else \
	  if test -n ""; then \
	    installdir="/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/tmp/main/usr/share/gtk-doc/html/vte-"; \
	  else \
	    installdir="/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/tmp/main/usr/share/gtk-doc/html/vte"; \
	  fi; \
	  /bin/sh /home/egon/warthogs/vte/build-area/vte-0.20.0/./mkinstalldirs ${installdir} ; \
	  for i in $installfiles; do \
	    echo '-- Installing '$i ; \
	    /usr/bin/install -c -m 644 $i ${installdir}; \
	  done; \
	  if test -n ""; then \
	    mv -f ${installdir}/vte.devhelp2 \
	      ${installdir}/vte-.devhelp2; \
	    mv -f ${installdir}/vte.devhelp \
	      ${installdir}/vte-.devhelp; \
	  fi; \
	   --relative --dest-dir=/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/tmp/main --html-dir=${installdir}; \
	fi
mkdir -p -- /home/egon/warthogs/vte/build-area/vte-0.20.0/debian/tmp/main/usr/share/gtk-doc/html/vte
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/ch01.html
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/home.png
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/index.html
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/index.sgml
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/left.png
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/right.png
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/style.css
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/up.png
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/vte.devhelp
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/vte.devhelp2
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/VteTerminalAccessible.html
-- Installing /home/egon/warthogs/vte/build-area/vte-0.20.0/./doc/reference/html/VteTerminal.html
/bin/sh: line 20: --relative: command not found
make[4]: *** [install-data-local] Error 127
make[4]: Leaving directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc/reference'
make[3]: *** [install-am] Error 2
make[3]: Leaving directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc/reference'
make[2]: *** [install-recursive] Error 1
make[2]: Leaving directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main/doc'
make[1]: *** [install-recursive] Error 1
make[1]: Leaving directory `/home/egon/warthogs/vte/build-area/vte-0.20.0/debian/build/main'
make: *** [common-install-impl] Error 2