bootloader: Set stage2_args:arguments_count when needed

src/system/boot/platform/bios_ia32/multiboot.cpp

@@ -56,6 +56,7 @@ parse_multiboot_commandline(stage2_args *args)
 
 	sArgs[0] = cmdline;
 	args->arguments = sArgs;
+	args->arguments_count = 1;
 
 	return B_OK;
 }

src/system/boot/platform/cfe/start.cpp

@@ -131,6 +131,7 @@ start(uint64 cfeHandle, uint64 cfeEntry)
 		static const char *sArgs[] = { NULL, NULL };
 		sArgs[0] = (const char *)bootargs;
 		args.arguments = sArgs;
+		args.arguments_count = 1;
 	}
 #endif
 

src/system/boot/platform/openfirmware/start.cpp

@@ -162,6 +162,7 @@ start(void *openFirmwareEntry)
 		static const char *sArgs[] = { NULL, NULL };
 		sArgs[0] = (const char *)bootargs;
 		args.arguments = sArgs;
+		args.arguments_count = 1;
 	}
 
 	determine_machine();