build: Fix nss code snippet includes

build: Fix nss code snippet includes

With hardened distribution CFLAGS the meson code snippet wouldn't compile:

Compiler stderr:
  .build/meson-private/tmpy2z1t5q4/testfile.c: In function 'main':
  .build/meson-private/tmpy2z1t5q4/testfile.c:2:30: error: storage size of 'hints' isn't known
      2 |              struct addrinfo hints, *result;
        |                              ^~~~~
  .build/meson-private/tmpy2z1t5q4/testfile.c:3:21: warning: implicit declaration of function 'getaddrinfo' [-Wimplicit-function-declaration]
      3 |              return getaddrinfo(argv[1], argv[2], &hints, &result);
        |                     ^~~~~~~~~~~