Enable Link-Time Optimization (LTO) to optimize the build

Packages describing “lto” as local USE flag

Package“lto” Flag Description
media-gfx/darktableEnable link-time optimisations in the RawSpeed library
sys-devel/binutils-appleAdd support for Link-Time Optimization with LLVM
sys-devel/gccBuild using Link Time Optimizations (LTO). Note that GCC is always built with support for building other programs with LTO. This USE flag is for whether GCC itself is built and optimized with LTO.
www-client/chromiumBuild with Link Time Optimizations (via clang's ThinLTO)
www-client/seamonkeyEnable Link Time Optimization (LTO). Requires Gold linker

All packages providing a “lto” USE flag (15)