make error: libwds/rtsp/gen directory not created

[lxrocks]

Getting the following error when running make on ubuntu 20.04. Seems like some files are not being generated. libwds/rtsp/gen directory is not created.

$ cmake .
-- Configuring done
-- Generating done
-- Build files have been written to: /home/minkley/minkProj/wds

$ make
[ 1%] [FLEX][HeaderLexer] Building scanner with flex 2.5.4
/opt/lampp/bin/flex: can't open header_
make[2]: *** [libwds/rtsp/CMakeFiles/wdsrtsp.dir/build.make:77: libwds/rtsp/gen/headerscanner.cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:311: libwds/rtsp/CMakeFiles/wdsrtsp.dir/all] Error 2
make: *** [Makefile:141: all] Error 2