Build error [use of undeclared identifier]with LLVM/icx (samples/net/nats)

[nashif]

Reported by ashish sinha:

Test case with build warnings raised from LLVM/icx: samples/net/nats

zephyr/subsys/net/ip/net_shell.c:1941:12: warning: 
      passing 'char *' to parameter of type 'const u8_t *' (aka
      'const unsigned char *') converts between pointers to integer types with
      different sign [-Wpointer-sign]
                                              argv[arg], TCP_TIMEOUT);
                                              ^~~~~~~~~
zephyr/include/net/net_pkt.h:912:23: note: passing
      argument to parameter 'data' here
                                      const u8_t *data, s32_t timeout)
                                                  ^
1 warning generated.
zephyr/samples/net/nats/src/main.c:236:28: error: use of
      undeclared identifier 'CONFIG_GPIO_QMSI_0_NAME'
        led0 = device_get_binding(LED_GPIO_NAME);
                                  ^
zephyr/samples/net/nats/src/main.c:18:23: note: expanded
      from macro 'LED_GPIO_NAME'
#define LED_GPIO_NAME LED0_GPIO_PORT
                      ^
zephyr/boards/x86/quark_se_c1000_devboard/board.h:21:25: note: 
      expanded from macro 'LED0_GPIO_PORT'
#define LED0_GPIO_PORT  CONFIG_GPIO_QMSI_0_NAME
                        ^
1 error generated.

How-to-reproduce: source zephyr-env.sh export ZEPHYR_GCC_VARIANT=issm cd samples/net/nats make pristine make BOARD=quark_se_c1000_devboard CC=icx

(Imported from Jira ZEP-2487)

[nashif]

by Jukka Rissanen:

I am fixing the warning currently and it will be fixed at the commit as GH-2319, but the error is another matter so modifying the title of the issue to reflect that.