ppc needs linking to libatomic

[barracuda156]

Same issue as here: https://github.com/Softmotions/iowow/issues/53

[355/368] : && /opt/local/bin/gcc-mp-12 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include                   -Wall                   -Wextra                   -Wfatal-errors                   -Wno-implicit-fallthrough                   -Wno-missing-braces                   -Wno-missing-field-initializers                   -Wno-sign-compare                   -Wno-unknown-pragmas                   -Wno-unused-function                   -Wno-unused-parameter                   -std=gnu11                   -fPIC -arch ppc -mmacosx-version-min=10.6 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-headerpad_max_install_names -L/opt/local/lib -lMacportsLegacySupport src/poller/tests/CMakeFiles/poller_pipe_test1.dir/poller_pipe_test1.c.o -o src/poller/tests/poller_pipe_test1  -Wl,-rpath,/opt/local/lib  src/libiwnet-1.a  /opt/local/lib/libiowow-1.a  -lm && :
FAILED: src/poller/tests/poller_pipe_test1 
: && /opt/local/bin/gcc-mp-12 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include                   -Wall                   -Wextra                   -Wfatal-errors                   -Wno-implicit-fallthrough                   -Wno-missing-braces                   -Wno-missing-field-initializers                   -Wno-sign-compare                   -Wno-unknown-pragmas                   -Wno-unused-function                   -Wno-unused-parameter                   -std=gnu11                   -fPIC -arch ppc -mmacosx-version-min=10.6 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-headerpad_max_install_names -L/opt/local/lib -lMacportsLegacySupport src/poller/tests/CMakeFiles/poller_pipe_test1.dir/poller_pipe_test1.c.o -o src/poller/tests/poller_pipe_test1  -Wl,-rpath,/opt/local/lib  src/libiwnet-1.a  /opt/local/lib/libiowow-1.a  -lm && :
Undefined symbols:
  "___atomic_fetch_xor_8", referenced from:
      _iwkvd_trigger_xor in libiowow-1.a(iwkv.c.o)
  "___atomic_load_8", referenced from:
      __onclosing in libiowow-1.a(iwal.c.o)
ld: symbol(s) not found
collect2: error: ld returned 1 exit status
[356/368] : && /opt/local/bin/gcc-mp-12 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include                   -Wall                   -Wextra                   -Wfatal-errors                   -Wno-implicit-fallthrough                   -Wno-missing-braces                   -Wno-missing-field-initializers                   -Wno-sign-compare                   -Wno-unknown-pragmas                   -Wno-unused-function                   -Wno-unused-parameter                   -std=gnu11                   -fPIC -arch ppc -mmacosx-version-min=10.6 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-headerpad_max_install_names -L/opt/local/lib -lMacportsLegacySupport src/poller/tests/CMakeFiles/poller_timeout_test1.dir/poller_timeout_test1.c.o -o src/poller/tests/poller_timeout_test1  -Wl,-rpath,/opt/local/lib  src/libiwnet-1.a  /opt/local/lib/libiowow-1.a  -lm && :
FAILED: src/poller/tests/poller_timeout_test1 
: && /opt/local/bin/gcc-mp-12 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include                   -Wall                   -Wextra                   -Wfatal-errors                   -Wno-implicit-fallthrough                   -Wno-missing-braces                   -Wno-missing-field-initializers                   -Wno-sign-compare                   -Wno-unknown-pragmas                   -Wno-unused-function                   -Wno-unused-parameter                   -std=gnu11                   -fPIC -arch ppc -mmacosx-version-min=10.6 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-headerpad_max_install_names -L/opt/local/lib -lMacportsLegacySupport src/poller/tests/CMakeFiles/poller_timeout_test1.dir/poller_timeout_test1.c.o -o src/poller/tests/poller_timeout_test1  -Wl,-rpath,/opt/local/lib  src/libiwnet-1.a  /opt/local/lib/libiowow-1.a  -lm && :
Undefined symbols:
  "___atomic_fetch_xor_8", referenced from:
      _iwkvd_trigger_xor in libiowow-1.a(iwkv.c.o)
  "___atomic_load_8", referenced from:
      __onclosing in libiowow-1.a(iwal.c.o)
ld: symbol(s) not found
collect2: error: ld returned 1 exit status