Compile failure on macOS platform

[cschol]

Cross-compilation with the Rack Plugin Toolchain fails on macOS platform:

src/Regex/Regex.cpp:32:41: error: reference to 'string' is ambiguous                                                                                       
                configSwitch(PARAM_MODE + i, 0, 1, 0, string::f("Mode %d", i + 1), {"Clock", "Pitch"});                                                    
                                                      ^                                                                                                    
src/Regex/../plugin.hpp:8:15: note: candidate found by name lookup is 'string'                                                                             
using                           std::string;                                                                                                               
                                     ^                                                                                                                     
/home/build/rack-plugin-toolchain/Rack-SDK-mac-x64/include/string.hpp:10:11: note: candidate found by name lookup is 'rack::string'                        
namespace string {                                                                                                                                         
          ^