On a Linux machine, build it and LD_PRELOAD it before your command.
$ cd ~/memtrace-interposer
$ make
$ cd ~/xlsynth
$ LD_PRELOAD=$HOME/memtrace-interposer/memtrace.so bazel-bin/xls/dslx/interpreter_main xls/dslx/stdlib/apfloat.x
$ python3 $HOME/memtrace-interposer/plot.py