Only build libjpeg test programs if libjpeg is actually available.

test/Makefile.am

-# TurboJPEG wrapper tests
 
+if HAVE_LIBJPEG
+# TurboJPEG wrapper tests
 noinst_PROGRAMS=tjunittest tjbench
-
 tjunittest_SOURCES=tjunittest.c ../common/turbojpeg.c ../common/turbojpeg.h \
 	tjutil.c tjutil.h
-
 tjbench_SOURCES=tjbench.c ../common/turbojpeg.c ../common/turbojpeg.h \
 	tjutil.c tjutil.h bmp.c bmp.h
 tjbench_LDADD=$(LDADD) -lm
+endif
 
 INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/common
 LDADD = ../libvncserver/libvncserver.la ../libvncclient/libvncclient.la @WSOCKLIB@