Emacs package does not build with gcc 14, which treats as errors a
number of situations which were only warnings before (see bug 1220571
for more details).  The error is:

xsettings.c: In function 'apply_xft_settings':
xsettings.c:846:25: error: implicit declaration of function 'round'
[-Wimplicit-function-declaration]
  846 |       oldsettings.dpi = round(oldsettings.dpi);
      |                         ^~~~~
xsettings.c:67:1: note: include '<math.h>' or provide a declaration of 'round'
   66 | #include <cairo/cairo-ft.h>
  +++ |+#include <math.h>
   67 | #endif

It seems that the problem comes from SUSE specific patch
emacs-25.1-custom-fonts.patch.  Adding #include <math.h> to it results in a
successfully finished build.

As of 10th April 2024, this can be conveniently tested locally with:
  osc build --alternative-project home:rguenther:nextgcc