libfox: compile with c++11 (#79667)
libfox: compile with c++11 (#79667)

Fixes:
2021-06-20T10:49:41.2440650Z ofx_utilities.cpp: In function ‘time_t ofxdate_to_time_t(const string&)’:
2021-06-20T10:49:41.2441563Z ofx_utilities.cpp:151:38: error: ‘nullptr’ was not declared in this scope
2021-06-20T10:49:41.2442666Z std::time_t temptime = std::time(nullptr);

This is needed on Linux for gcc-5, but I enabled it for mac too,
as this should do no harm there
nandub/homebrew-core,mfikes/homebrew-core,stgraber/homebrew-core,mfikes/homebrew-core,uyjulian/homebrew-core,lemzwerg/homebrew-core,Homebrew/homebrew-core,stgraber/homebrew-core,cblecker/homebrew-core,Homebrew/homebrew-core,mbcoguno/homebrew-core,sjackman/homebrew-core,nbari/homebrew-core,lemzwerg/homebrew-core,zyedidia/homebrew-core,sjackman/homebrew-core,Moisan/homebrew-core,mbcoguno/homebrew-core,zyedidia/homebrew-core,uyjulian/homebrew-core,nbari/homebrew-core,Linuxbrew/homebrew-core,filcab/homebrew-core,cblecker/homebrew-core,chrisfinazzo/homebrew-core,filcab/homebrew-core,makigumo/homebrew-core,adam-moss/homebrew-core,mbcoguno/homebrew-core,nandub/homebrew-core,makigumo/homebrew-core,chrisfinazzo/homebrew-core,Linuxbrew/homebrew-core,Moisan/homebrew-core,adam-moss/homebrew-core