Fix compiling on OpenBSD

Avoid use of undeclared identifier `ELFOSABI_AIX`.

For the reference, see:
 - https://codeberg.org/OpenBSD/ports/src/commit/c5e4088b89277b96d840492f9961b1593182b99c/x11/qt6/qtbase/patches/patch-src_corelib_plugin_qelfparser_p_cpp


--- a/qtbase/src/corelib/plugin/qelfparser_p.cpp
+++ b/qtbase/src/corelib/plugin/qelfparser_p.cpp
@@ -341,7 +341,9 @@ Q_DECL_UNUSED Q_DECL_COLD_FUNCTION static QDebug &operator<<(QDebug &d, ElfHeade
     case ELFOSABI_NETBSD:   d << " (NetBSD"; break;
     case ELFOSABI_LINUX:    d << " (GNU/Linux"; break;
     case ELFOSABI_SOLARIS:  d << " (Solaris"; break;
+#ifndef Q_OS_OPENBSD
     case ELFOSABI_AIX:      d << " (AIX"; break;
+#endif
     case ELFOSABI_IRIX:     d << " (IRIX"; break;
     case ELFOSABI_FREEBSD:  d << " (FreeBSD"; break;
     case ELFOSABI_OPENBSD:  d << " (OpenBSD"; break;