Bug 1225908

GCC 14 newly by default treats as errors a number of situations which
before were only warnings.  For more information see
https://gcc.gnu.org/gcc-14/porting_to.html and meta bug #1220571.

Because of this, package osinfo-db-tools fails to compile.  This can be seen online
at:
https://build.opensuse.org/package/live_build_log/openSUSE:Factory:Staging:Gcc7/osinfo-db-tools/standard/x86_64

It can be reproduced locally with command: osc build --clean
--alternative-project home:rguenther:nextgcc


The (first) error (that halts the build) is:

[   11s] ../tools/osinfo-db-validate.c: In function ‘validate_files’:
[   11s] ../tools/osinfo-db-validate.c:176:37: error: passing argument 2 of ‘xmlSetStructuredErrorFunc’ from incompatible pointer type [-Wincompatible-pointer-types]
[   11s]   176 |     xmlSetStructuredErrorFunc(NULL, validate_structured_error_nop);
[   11s]       |                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[   11s]       |                                     |
[   11s]       |                                     void (*)(void *, xmlError *) {aka void (*)(void *, struct _xmlError *)}
[   11s] In file included from /usr/include/libxml2/libxml/relaxng.h:14,
[   11s]                  from ../tools/osinfo-db-validate.c:23:
[   11s] /usr/include/libxml2/libxml/xmlerror.h:898:57: note: expected ‘xmlStructuredErrorFunc’ {aka ‘void (*)(void *, const struct _xmlError *)’} but argument is of type ‘void (*)(void *, xmlError *)’ {aka ‘void (*)(void *, struct _xmlError *)’}
[   11s]   898 |                                  xmlStructuredErrorFunc handler);
[   11s]       |                                  ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~