spirv: switch to util_bswap32 to improve portability
Regressed by !6090 (merged). See error log and downstream fix. CC @pkubaj who helped with testing.
Each OS tends to have slightly different naming for byteswap functions:
- Linux (bionic, glibc, musl) use
bswap_32
- FreeBSD and NetBSD use
bswap32
- OpenBSD use
swap32
Each OS defines byteswap functions in different headers:
- Linux (bionic, glibc, musl) use
<byteswap.h>
- FreeBSD and OpenBSD use
<sys/endian.h>
- NetBSD uses
<sys/bswap.h>
(but<sys/endian.h>
can also be used)