target/loongarch: 'make check-tcg' support

Signed-off-by: Song Gao <gaosong@loongson.cn>
Signed-off-by: Xiaojuan Yang <yangxiaojuan@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220606124333.2060567-44-yangxiaojuan@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

configure

@@ -1831,6 +1831,7 @@ fi
 : ${cross_prefix_arm="arm-linux-gnueabihf-"}
 : ${cross_prefix_armeb="$cross_prefix_arm"}
 : ${cross_prefix_hexagon="hexagon-unknown-linux-musl-"}
+: ${cross_prefix_loongarch64="loongarch64-unknown-linux-gnu-"}
 : ${cross_prefix_hppa="hppa-linux-gnu-"}
 : ${cross_prefix_i386="i686-linux-gnu-"}
 : ${cross_prefix_m68k="m68k-linux-gnu-"}