build: Cleanup libxkbcommon_postprocess_cmds

There is no "share" directory in the staging one.

depends/packages/libxkbcommon.mk

@@ -27,6 +27,6 @@ define $(package)_stage_cmds
 endef
 
 define $(package)_postprocess_cmds
-  rm -rf share/man share/doc lib/*.la
+  rm lib/*.la
 endef