Add CXXFLAGS to fix build failure on armel.

debian/changelog

@@ -2,6 +2,7 @@ qt6-base (6.3.1+dfsg-2) UNRELEASED; urgency=medium
 
   [ Patrick Franz ]
   * Update symbols from buildlogs.
+  * Add CXXFLAGS to fix build failure on armel.
 
  -- Debian Qt/KDE Maintainers <debian-qt-kde@lists.debian.org>  Sat, 16 Jul 2022 01:58:16 +0200
 

debian/rules

@@ -19,6 +19,9 @@ else
         extra_cmake_args += -DFEATURE_sctp=OFF
 endif
 
+# Prevent "Error: selected processor does not support `yield' in ARM mode"
+export DEB_CXXFLAGS_MAINT_APPEND = -march=native -mcpu=native
+
 %:
 	dh $@ --with pkgkde_symbolshelper --buildsystem=cmake+ninja