Today, Wine fails to build with musl libc and Linux kernel 5.14 uAPI header files.
musl libc doesn't supply any definitions for IPX, such as the SOL_IPX macro. However, it still provides linux/ipx.h from Linux uAPI header files if it exists.
Linux kernel wouldn't drop linux/ipx.h from uAPI headers until 5.15, although IPX support has already been marked obsolete since 2018.
Fix this by not defining HAS_IPX if linux/ipx.h has been included but nothing defines the SOL_IPX macro.
Status of IPX support from other libcs are noted below:
- bionic: netipx/ipx.h does not exist. linux/ipx.h may or may not exist. Note that sys/socket.h defines SOL_IPX even if linux/ipx.h is missing.
- glibc: netipx/ipx.h exists. In this case, Wine assumes IPX support even if the operating system does not support it in runtime.
- BSD variants: netipx/ipx.h may or may not exist. linux/ipx.h does not exist. Some BSDs supply SO_DEFAULT_HEADERS instead of SOL_IPX.
-- v2: server: Avoid relying on linux/ipx.h to define SOL_IPX. ws2_32: Avoid relying on linux/ipx.h to define SOL_IPX. ntdll: Avoid relying on linux/ipx.h to define SOL_IPX.