Autoconf 2.72 (or 2.73) seems to be under preparation upstream, I therefore started to build dependent components against the pre-release [1] to verify that they can be built once it lands in Fedora.

Your component fails to build with the new version of autoconf, due to the following error:

./configure: line 27629: syntax error near unexpected token `fi'
./configure: line 27629: `fi'
error: Bad exit status from /var/tmp/rpm-tmp.eXf7IP (%build)

This error is due to a misplaced 'fi' in acinclude.m4. While this always has been wrong, older version of autoconf didn´t lead to an error by luck.
The following patch is a fix proposal.

---
diff -r -U5 kguitar.old/admin/acinclude.m4.in kguitar/admin/acinclude.m4.in
--- kguitar.old/admin/acinclude.m4.in	2023-03-30 17:32:58.447408658 +0200
+++ kguitar/admin/acinclude.m4.in	2023-03-30 17:33:34.905478568 +0200
@@ -2539,12 +2539,12 @@
             eval "kde_cv_qt_jpeg=no",
             eval "kde_cv_qt_jpeg=yes")
 LIBS="$ac_save_LIBS"
 CXXFLAGS="$ac_save_CXXFLAGS"
 AC_LANG_RESTORE
-fi
 ])
+fi
 
 if eval "test ! \"`echo $kde_cv_qt_jpeg`\" = no"; then
   AC_MSG_RESULT(yes)
   LIBJPEG_QT='$(LIBJPEG)'
 else
---

Please forward this to the community, and update the component accordingly.

[1] https://lists.gnu.org/archive/html/autoconf/2023-03/msg00020.html