Snippets for msgpack-c 6.1.0 from Alpine s390x

Sourced from https://build.alpinelinux.org/buildlogs/build-edge-s390x/community/msgpack-c/msgpack-c-6.1.0-r1.log.

• /home/buildozer/aports/community/msgpack-c/src/msgpack-c-6.1.0/example/boundary.c:51:16: warning: unused variable 'len' [-Wunused-variable]
     51 |         size_t len = strlen(#b);                             \
        |                ^~~
  

• /home/buildozer/aports/community/msgpack-c/src/msgpack-c-6.1.0/example/boundary.c:185:16: warning: unused variable 'len' [-Wunused-variable]
    185 |         size_t len = strlen(#b);                             \
        |                ^~~
  

• /home/buildozer/aports/community/msgpack-c/src/msgpack-c-6.1.0/example/boundary.c:39:12: warning: variable 'offset' set but not used [-Wunused-but-set-variable]
     39 |     size_t offset = 0;
        |            ^~~~~~
  

• /home/buildozer/aports/community/msgpack-c/src/msgpack-c-6.1.0/build/include/msgpack/pack_template.h:885:39: warning: conversion from 'size_t' {aka 'long unsigned int'} to 'uint16_t' {aka 'short unsigned int'} may change value [-Wconversion]
    885 |             _msgpack_store16(&buf[1], l);
  

• /home/buildozer/aports/community/msgpack-c/src/msgpack-c-6.1.0/build/include/msgpack/pack_template.h:891:39: warning: conversion from 'size_t' {aka 'long unsigned int'} to 'uint32_t' {aka 'unsigned int'} may change value [-Wconversion]
    891 |             _msgpack_store32(&buf[1], l);