gnome-builder 3.26.4 release, together with required libdazzle update.

Changes in gnome-builder 3.26.4:

• A number of correctness and memory leaks were fixed in the semantic highlighter, project tree, clang, rustup, vala-pack, code-index, config manager and configs, and git.
• The meson plugin now uses "meson" "introspect" instead of the legacy "mesonintrospect" utility.
• Fixes for deprecated API usage in Gtk+.
• Block selection has been fixed in the terminal plugin.
• Postbuild support in configurations was fixed to no longer run prebuild commands a second time.
• The flatpak plugin now passes --command to build-finish. This fixes an issue where the wrong binary would get activated when exporting a project.
• Fixes for -Wincompatible-pointer-type changes from recently upstreamed type propagation in g_object_ref().

Changes in libdazzle 3.26.3:

• A number of fixes to DzlSignalGroup to be more re-entrant safe and handle disposal cycles better.
• DzlPreferences is more aggressive about protecting against widget disposal.
• A static inline dzl_clear_signal_handler() was backported for use in other backports from master.
• A number of protections were added to DzlDirectoryReaper to protect against potentially following through symlinks.
• Max age in DzlDirectoryReaper was changed to always ensure a positive value for use in date comparisons.
• A leak of GFile instances in the directory reaper was fixed.