gentoo-overlay/dev-lang/rust/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <maintainer type="project">
    <email>rust@gentoo.org</email>
    <name>Rust Project</name>
  </maintainer>
  <use>
    <flag name="clang">Use <pkg>sys-devel/clang</pkg> for building</flag>
    <flag name="libcxx">Use <pkg>sys-libs/libcxx</pkg> as standard
    library when building with <pkg>sys-devel/clang</pkg></flag>
    <flag name="system-llvm">Use system <pkg>sys-devel/llvm</pkg> in
    place of the bundled one</flag>
    <flag name="jemalloc">Use <pkg>sys-libs/jemalloc</pkg> as the
    standard memory allocator</flag>
  </use>
</pkgmetadata>