GCC 12 gives -Wimplicit-fallthrough because of -Wextra

[mjakubicek]

Either you should remove -Wextra or add the __attribute__ ((fallthrough)) to suppress it.

murmurhash3.c: In function ‘hash’:
murmurhash3.c:62:20: warning: this statement may fall through [-Wimplicit-fallthrough=]
   62 |         case 3: k1 ^= tail[2] << 16;
      |                 ~~~^~~~~~~~~~~~~~~~
murmurhash3.c:63:9: note: here
   63 |         case 2: k1 ^= tail[1] << 8;
      |         ^~~~
murmurhash3.c:63:20: warning: this statement may fall through [-Wimplicit-fallthrough=]
   63 |         case 2: k1 ^= tail[1] << 8;
      |                 ~~~^~~~~~~~~~~~~~~
murmurhash3.c:64:9: note: here
   64 |         case 1: k1 ^= tail[0];
      |         ^~~~