Global USE flags

Flag Description Packages
debug Enable debug logging and the --debug command-line option. 2

Local USE flags

app-arch

innoextract

Flag Description
iconv
lzma Enable support for extracting lzma-compressed installers using <pkg>app-arch/xz-utils</pkg>.

games-rpg

arx-fatalis-data

Flag Description
cdinstall
french Use the French version of the GOG.com installer.
german Use the German version of the GOG.com installer.
gog Extract the data from the GOG.com installer.
italian Use the Italian version of the GOG.com installer.
russian Use the Russian version of the GOG.com installer.
spanish Use the Spanish version of the GOG.com installer.

arx-libertatis

Flag Description
X
blender Install the Arx Libertatis Blender addon and support library.
crash-reporter Build a <pkg>dev-qt/qtgui</pkg>-based tool that allows to submit crash information to the upstream backtracker.
custom-optimization Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3, etc) from CFLAGS
sdl2 Build against <pkg>media-libs/libsdl2</pkg> instead of <pkg>media-libs/libsdl</pkg>.
static Link libraries statically, currently only <pkg>sys-libs/zlib</pkg>, <pkg>media-libs/glew</pkg> and <pkg>media-libs/freetype</pkg> (including <pkg>media-libs/libpng</pkg> and <pkg>app-arch/bzip2</pkg> if FreeType is built with them)
test
tools Build tools that can extract the game's data and save files.
unity-build Build everything in one big source file, allowing for faster build times and better optimizations at the cost of higher memory usage.
wayland