Add support for LoongArch.

Signed-off-by: liuxiang <liuxiang@loongson.cn>

config/architectures.yaml

@@ -53,6 +53,10 @@ autodetect:
     name: RISC-V 64-bit
     check: DUK_F_RISCV64
     include: architecture_riscv64.h.in
+  -
+    name: LOONGARCH 64-bit
+    check: DUK_F_LOONGARCH64
+    include: architecture_loongarch64.h.in
   -
     name: SuperH
     check: DUK_F_SUPERH

config/architectures/architecture_loongarch64.h.in

@@ -0,0 +1,3 @@
+#define DUK_USE_ARCH_STRING "loongarch64"
+#define DUK_USE_BYTEORDER 1
+#undef DUK_USE_PACKED_TVAL

config/helper-snippets/DUK_F_LOONGARCH.h.in

@@ -0,0 +1,4 @@
+/* LOONGARCH64, https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html */
+#if defined(__loongarch64)
+#define DUK_F_LOONGARCH64
+#endif