test-spa-json exits with SIGSEGV on aarch64, ppc64le and x86 (Alpine Linux, Musl libc)

This happens with the 0.4.8 release.

Summary of Failures:
 9/24 test-spa-json          FAIL            0.18s   killed by signal 11 SIGSEGV
Ok:                 23  
Expected Fail:      0   
Fail:               1   
Unexpected Pass:    0   
Skipped:            0   
Timeout:            0

All other arches (armhf, armv7, x86_64, riscv64) have this test succeeding perfectly fine.