a.rb

$ ninja examples
[5/6] LINK obj/examples/example1.o
FAILED: g++ -Wall -Wextra -pedantic -Werror -std=c++11 -g -flto obj/examples/example1.o -o bin/examples/example1 -lboost_system
Undefined symbols for architecture x86_64:
  "__istype(int, unsigned long)", referenced from:
      std::ctype<char>::is(unsigned long, char) const in example1.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
[5/6] LINK obj/examples/example2.o
FAILED: g++ -Wall -Wextra -pedantic -Werror -std=c++11 -g -flto obj/examples/example2.o -o bin/examples/example2 -lboost_system
Undefined symbols for architecture x86_64:
  "__istype(int, unsigned long)", referenced from:
      std::ctype<char>::is(unsigned long, char) const in example2.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
[5/6] C++ 'examples/example3.c++'
ninja: build stopped: subcommand failed.