astro/gpscorrelate: fix build with GCC-based architectures

Add USES=compiler:c++11-lang:
/usr/local/lib/libexiv2.so: undefined reference to `std::__cxx11::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >::basic_ostringstream(std::_Ios_Openmode)@GLIBCXX_3.4.21'

Approved by: mentors (implicit approval)