Add support for loongarch64-unknown-linux-gnu target (alexcrichton#189)

Author: heiher

src/lib.rs

@@ -264,6 +264,7 @@ impl Build {
             "i686-unknown-freebsd" => "BSD-x86-elf",
             "i686-unknown-linux-gnu" => "linux-elf",
             "i686-unknown-linux-musl" => "linux-elf",
+            "loongarch64-unknown-linux-gnu" => "linux64-loongarch64",
             "mips-unknown-linux-gnu" => "linux-mips32",
             "mips-unknown-linux-musl" => "linux-mips32",
             "mips64-unknown-linux-gnuabi64" => "linux64-mips64",