build fails on CentOS 7

  :
Making all in test
make[2]: Entering directory `/home/rdt/src/dillo-3.0.4/test'
g++ -DHAVE_CONFIG_H -I. -I..  -I.. -I/usr/local/include -I/usr/include/freetype2 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_THREAD_SAFE -D_REENTRANT -g -O2 -Wall -W -Wno-unused-parameter -fno-rtti -fno-exceptions -MT dw_anchors_test.o -MD -MP -MF .deps/dw_anchors_test.Tpo -c -o dw_anchors_test.o dw_anchors_test.cc
mv -f .deps/dw_anchors_test.Tpo .deps/dw_anchors_test.Po
g++ -I/usr/include/freetype2 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_THREAD_SAFE -D_REENTRANT -g -O2 -Wall -W -Wno-unused-parameter -fno-rtti -fno-exceptions  -L/usr/local/lib -o dw-anchors-test dw_anchors_test.o ../dw/libDw-widgets.a ../dw/libDw-fltk.a ../dw/libDw-core.a ../lout/liblout.a -Wl,-z,relro -lfltk 
/bin/ld: ../dw/libDw-fltk.a(libDw_fltk_a-fltkviewbase.o): undefined reference to symbol 'XCreatePixmap'
/bin/ld: note: 'XCreatePixmap' is defined in DSO /lib64/libX11.so.6 so try adding it to the linker command line
/lib64/libX11.so.6: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
make[2]: *** [dw-anchors-test] Error 1
make[2]: Leaving directory `/home/rdt/src/dillo-3.0.4/test'

Bob T.