libxkbcommon: enable xkbregistry for plasma-desktop

plasma-desktop requires it unconditionally:
  CMakeLists.txt:244  pkg_check_modules(XKBREGISTRY xkbregistry REQUIRED ...)
and configure aborted with "The following required packages were not found:
- xkbregistry". The recipe had -Denable-xkbregistry=false.

xkbregistry provides the keyboard-layout registry the keyboard KCM reads, so
this restores a real feature rather than routing around one. Its dependency,
libxml2, was already in the tree (recipes/libs/libxml2) and is now declared and
added to the config.

-Denable-x11 is deliberately left false for now: it is a separate switch, not
required by this failure, and turning it on alongside would blur which change
fixed what if the rebuild misbehaves.

config/redbear-full.toml

@@ -138,6 +138,7 @@ libdrm = {}
 
 # X11 protocol headers (needed by libxau, libxkbcommon, xwayland)
 x11proto = {}
+libxml2 = {}
 libxkbcommon = {}
 xkeyboard-config = {}
 

local/recipes/libs/libxkbcommon/recipe.toml

@@ -9,11 +9,17 @@ mesonflags = [
     "-Denable-x11=false",
     "-Denable-tools=false",
     "-Denable-docs=false",
-    "-Denable-xkbregistry=false",
+    # xkbregistry ENABLED: plasma-desktop requires it unconditionally
+    # (CMakeLists.txt:244, pkg_check_modules(XKBREGISTRY ... REQUIRED)), and
+    # without it configure aborts. It provides the keyboard-layout registry the
+    # keyboard KCM reads. Needs libxml2, which is in tree.
+    "-Denable-xkbregistry=true",
     "-Dxkb-config-root=/usr/share/X11/xkb",
     "-Dx-locale-root=/usr/share/X11/locale",
 ]
 dependencies = [
+    # required by -Denable-xkbregistry=true
+    "libxml2",
     "libwayland",
     "wayland-protocols",
     "xkeyboard-config",