make failing at 99%

[RedactedCode]

Puppy Linux "FOSSA64" (essentially a Ubuntu derivative)
CDP8 cloned from github (default)
libaaio built from supplied tar & installed OK
portaudio 19.6 already installed, also installed portaudio-dev19 from repo.

cmake runs ok
make runs ok with a small number of warnings only, but fails at the following point:

Scanning dependencies of target listaudevs
[ 99%] Building C object dev/externals/paprogs/listaudevs/CMakeFiles/listaudevs.dir/devs.c.o
[ 99%] Linking C executable ../../../../../NewRelease/listaudevs
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libportaudio.a(pa_jack.o): undefined reference to symbol 'pthread_mutex_trylock@@GLIBC_2.2.5'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libpthread.so: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [dev/externals/paprogs/listaudevs/CMakeFiles/listaudevs.dir/build.make:85: ../NewRelease/listaudevs] Error 1
make[1]: *** [CMakeFiles/Makefile2:8025: dev/externals/paprogs/listaudevs/CMakeFiles/listaudevs.dir/all] Error 2
make: *** [Makefile:152: all] Error 2

There is a thread at SO https://stackoverflow.com/questions/34143265/undefined-reference-to-symbol-pthread-createglibc-2-2-5 regarding a very similar error. but adding the suggested SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread") to
CMakeLists.txt in the top level of the CDP8 directory didn't make a difference. The compile failed at the same place again