`make check` fails on osx

[Andy Alt]

As of the last commit, make check now fails on osx.

Making check in man

make[1]: Nothing to be done for `check'.

Making check in tests

/Applications/Xcode-10.1.app/Contents/Developer/usr/bin/make  getNumArg connect

  CC       getNumArg.o

  CCLD     getNumArg

Undefined symbols for architecture x86_64:

  "_cmdarg", referenced from:

      _atcmdInit in getNumArg.o

  "_telOpt", referenced from:

      _prOption in getNumArg.o

      _atcmdPB in getNumArg.o

      _atcmdPL in getNumArg.o

      _sockDial in libmodemu2k_test.a(libmodemu2k_test_a-sock.o)

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

make[2]: *** [getNumArg] Error 1

make[1]: *** [check-am] Error 2

make: *** [check-recursive] Error 1

The command "if [ -z "$CHECK" ]; then make check; else make distcheck; fi" exited with 2.
cache.2

store build cache

Log:
https://travis-ci.org/github/theimpossibleastronaut/modemu2k/jobs/699573471