ncurses: Pin to C17 standard

Newer snapshots of ncurses have the fixes but they are many needed to get
C23 going. Until next release lets stick with C17 even while GCC 15 switches
to C23 defaults.

(From OE-Core rev: f3081700d931fc8f7d5cb13494e11100cb28b19f)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/ncurses/ncurses.inc

@@ -28,6 +28,9 @@ ENABLE_WIDEC ?= "true"
 # _GNU_SOURCE is required for widec stuff and is not detected automatically
 CPPFLAGS += "-D_GNU_SOURCE"
 
+# Check if we still need it when next release (6.6) happens
+CFLAGS += "-std=gnu17"
+
 # natives don't generally look in base_libdir
 base_libdir:class-native = "${libdir}"