rules: enforce system libb2

debian/changelog

@@ -6,6 +6,8 @@ qt6-base (6.2.2+dfsg-4) UNRELEASED; urgency=medium
   * Replace patch path_max.diff with upstream commit
     7c54988b1b3b9eb4d2f3650c1ba5ffe97673ca92; patch
     upstream_Avoid-a-stack-buffer-when-not-needed.patch.
+  * Pass -DFEATURE_system_libb2=ON to cmake to make sure the system blake2
+    implementation (libb2) is used instead of the embedded copy.
 
  -- Debian Qt/KDE Maintainers <debian-qt-kde@lists.debian.org>  Thu, 10 Feb 2022 07:33:31 +0100
 

debian/rules

@@ -68,6 +68,7 @@ override_dh_auto_configure:
 		-DFEATURE_system_jpeg=ON \
 		-DFEATURE_png=ON \
 		-DFEATURE_system_png=ON \
+		-DFEATURE_system_libb2=ON \
 		-DCMAKE_BUILD_RPATH_USE_ORIGIN=ON \
 		$(extra_cmake_args)