hard code deployment target for now

Author: wolfv

vinca/templates/build_ament_cmake.sh.in

@@ -23,6 +23,7 @@ cmake \
     -DCMAKE_INSTALL_SYSTEM_RUNTIME_LIBS_SKIP=True \
     -DBUILD_SHARED_LIBS=ON  \
     -DBUILD_TESTING=OFF \
+    -DCMAKE_OSX_DEPLOYMENT_TARGET=10.12 \
     $SRC_DIR/$PKG_NAME/src/work
 
 cmake --build . --config Release --target install