Fix detection of XOPEN_SOURCE

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Upstream: fixed in latest release, no git/svn/hg

diff -Nur ncurses-snapshots-6_4_20230603.orig/configure ncurses-snapshots-6_4_20230603/configure
--- ncurses-snapshots-6_4_20230603.orig/configure	2023-06-04 00:07:40.000000000 +0200
+++ ncurses-snapshots-6_4_20230603/configure	2024-08-14 20:38:03.426905460 +0200
@@ -10411,7 +10411,7 @@
 	cf_xopen_source="-D_SGI_SOURCE"
 	cf_XOPEN_SOURCE=
 	;;
-(linux*gnu|linux*gnuabi64|linux*gnuabin32|linux*gnueabi|linux*gnueabihf|linux*gnux32|uclinux*|gnu*|mint*|k*bsd*-gnu|cygwin|msys|mingw*)
+(linux*gnu|linux*gnuabi64|linux*gnuabin32|linux*gnueabi|linux*gnueabihf|linux*gnux32|uclinux*|gnu*|mint*|k*bsd*-gnu|cygwin|msys|mingw*|linux*uclibc)
 
 cf_gnu_xopen_source=$cf_XOPEN_SOURCE