CMake: Clean up run_pzip

This should get rid of stray directories in the build
directory on Windows.

cmake/macros/RunPzip.cmake

@@ -10,20 +10,23 @@ function(run_pzip target_name source destination glob)
   file(GLOB_RECURSE files RELATIVE "${source}" "${source}/${glob}")
 
   set(dstfiles "")
-  foreach(srcfile ${files})
-    file(RELATIVE_PATH srcfile_rel "${destination}" "${source}/${srcfile}")
-    file(RELATIVE_PATH dstfile_rel "${destination}" "${destination}/${srcfile}.pz")
+  foreach(filename ${files})
+    string(REGEX REPLACE "^/" "" filename "${filename}")
+    file(RELATIVE_PATH srcfile "${destination}" "${source}/${filename}")
 
-    list(APPEND dstfiles "${dstfile_rel}")
-    add_custom_command(OUTPUT "${dstfile_rel}"
-      COMMAND pzip -c > "${dstfile_rel}" < "${srcfile_rel}"
+    get_filename_component(dstdir "${destination}/${filename}" DIRECTORY)
+    file(MAKE_DIRECTORY "${dstdir}")
+
+    set(dstfile "${filename}.pz")
+    list(APPEND dstfiles "${destination}/${dstfile}")
+
+    add_custom_command(OUTPUT "${destination}/${dstfile}"
+      COMMAND pzip -c > "${dstfile}" < "${srcfile}"
       WORKING_DIRECTORY "${destination}"
       DEPENDS pzip
       COMMENT "")
 
-    get_filename_component(dstdir "${destination}/${dstfile_rel}" DIRECTORY)
-    file(MAKE_DIRECTORY "${dstdir}")
-  endforeach(srcfile)
+  endforeach(filename)
 
   add_custom_target(${target_name} ALL
     DEPENDS ${dstfiles}