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. https://gitlab.winehq.org/wine/wine/-/merge_requests/3428