add support for a new architecture loongarch

c_src/double-conversion/utils.h

@@ -94,6 +94,7 @@ int main(int argc, char** argv) {
     defined(__ARMEL__) || defined(__avr32__) || defined(_M_ARM) || defined(_M_ARM64) || \
     defined(__hppa__) || defined(__ia64__) || \
     defined(__mips__) || \
+    defined(__loongarch__) \
     defined(__powerpc__) || defined(__ppc__) || defined(__ppc64__) || \
     defined(_POWER) || defined(_ARCH_PPC) || defined(_ARCH_PPC64) || \
     defined(__sparc__) || defined(__sparc) || defined(__s390__) || \