Build fails: "./test.sh: line 49: shunit2: No such file or directory"

On stock Sonoma, building byte words-cli fails with "./test.sh: line 49: shunit2: No such file or directory"

```
bytewords-cli % ./build.sh
…
cd src && /Library/Developer/CommandLineTools/usr/bin/make check
c++ -I/Users/christophera/WIP/Workspace/github/blockchaincommons/bytewords-cli/sysroot/include -std=c++17 --debug -O0 -I"../deps/cbor-lite/include" -c -o bytewords.o bytewords.cpp
c++ -I/Users/christophera/WIP/Workspace/github/blockchaincommons/bytewords-cli/sysroot/include -std=c++17 --debug -O0 -I"../deps/cbor-lite/include" -c -o utils.o utils.cpp
c++ -I/Users/christophera/WIP/Workspace/github/blockchaincommons/bytewords-cli/sysroot/include -std=c++17 --debug -O0 -I"../deps/cbor-lite/include" -c -o params.o params.cpp
cc -L/Users/christophera/WIP/Workspace/github/blockchaincommons/bytewords-cli/sysroot/lib bytewords.o utils.o params.o -lstdc++ -lbc-bytewords -largp -lbc-crypto-base -lstdc++ -o bytewords
ld: warning: ignoring duplicate libraries: '-lc++'
./test.sh ./bytewords
./test.sh: line 49: shunit2: No such file or directory
make[1]: *** [check] Error 1
make: *** [check] Error 2
```