MFH: r545302

deskutils/terminal-image-viewer: fix build on GCC architectures

-lstdc++fs is necessary for GCC:
/usr/local/bin/ld: tiv.cpp:(.text.startup+0x19cc): undefined reference to `std::experimental::filesystem::v1::__cxx11::directory_iterator::operator++()'

Approved by: portmgr (fix build blanket)