devel/android-tools-fastboot-devel: unbreak build on DragonFly (like r400822)

fastboot.o:fastboot.cpp:function std::_Function_handler<void (std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&), main::{lambda(std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)#1}>::_M_invoke(std::_Any_data const&, std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&): error: undefined reference to 'fs_get_generator(std::cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
fastboot.o:fastboot.cpp:function fb_perform_format(Transport*, char const*, int, char const*, char const*) [clone .constprop.79]: error: undefined reference to 'fs_get_generator(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)'
fastboot.o:fastboot.cpp:function fb_perform_format(Transport*, char const*, int, char const*, char const*) [clone .constprop.79]: error: undefined reference to 'fs_generator_generate(fs_generator const*, int, long long)'

Reported by: muscles.dragonflybsd.org