$ pwd
/usr/home/dbb/src/postgis_21
$ ls doc
Makefile			html				reference_operator.xml
Makefile.comments		installation.xml		reference_output.xml
Makefile.comments.in		introduction.xml		reference_processing.xml
Makefile.in			man				reference_raster.xml
README				performance_tips.xml		reference_sfcgal.xml
ZMSgeoms.txt			po				reference_transaction.xml
bnf-wkb.txt			postgis.xml			reference_type.xml
bnf-wkt.txt			reference.xml			release_notes.xml
doxygen.cfg.in			reference_accessor.xml		reporting.xml
extras.xml			reference_constructor.xml	rfc
extras_historytable.xml		reference_editor.xml		template.xml
extras_tigergeocoder.xml	reference_exception.xml		using_postgis_app.xml
extras_topology.xml		reference_lrs.xml		using_postgis_dataman.xml
faq.xml				reference_management.xml	using_raster_dataman.xml
faq_raster.xml			reference_measure.xml		xmlformat.conf
geography.txt			reference_misc.xml		xsl
$ cd doc
$ make
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 30: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 32: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 34: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 49: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 51: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 94: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 96: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 98: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 100: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 165: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 167: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 170: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 292: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 294: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 296: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 300: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 309: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 311: warning: duplicate script for target "comments-install" ignored
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 308: warning: using previous script for "comments-install" defined here
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 312: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 343: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 345: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 349: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 353: Missing dependency operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 355: Need an operator
make: "/usr/home/dbb/src/postgis_21/doc/Makefile" line 358: Need an operator
make: Fatal errors encountered -- cannot continue
make: stopped in /usr/home/dbb/src/postgis_21/doc
$