Implement sysconf(_SC_ARG_MAX) syscall

Author: LLONSIT

dtc

@@ -267,6 +267,7 @@
 
 
 /* syssgi(sysconf, cmd, ...) */
+#define TARGET_NR_sysconf_argmax    (1)
 #define TARGET_NR_sysconf_childmax	(2)
 #define TARGET_NR_sysconf_clktick	(3)
 #define TARGET_NR_sysconf_openmax	(5)

linux-user/irix/syscall_nr.h

@@ -14520,6 +14520,9 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             case TARGET_NR_sysconf_mac:
                 ret = 0;
                 break;
+            case TARGET_NR_sysconf_argmax:
+                ret = get_errno(sysconf(_SC_ARG_MAX));
+                break;
             default:
                 gemu_log("qemu: Unsupported syscall: sysconf(%d)\n", (int)arg2);
                 ret = -TARGET_ENOSYS;