build-pkg: log and remove empty directories

tools/build-pkg.lua

@@ -531,6 +531,22 @@ local function checkFileList(files, item)
     end
 end
 
+local function removeEmptyDirs(item)
+    -- removing an empty dir can reveal another one (parent)
+    local go_on = true
+    while go_on do
+        go_on = false
+        local f = io.popen('find usr/* -empty -type d', 'r')
+        for dir in f:lines() do
+            log("Remove empty directory %s created by %s",
+                dir, item)
+            os.remove(dir)
+            go_on = true
+        end
+        f:close()
+    end
+end
+
 -- builds package, returns list of new files
 local function buildItem(item, item2deps, file2item, item2index)
     gitCheckout(itemToBranch(item), item2deps[item], item2index)
@@ -557,6 +573,7 @@ local function buildItem(item, item2deps, file2item, item2index)
             item, file, creator_item)
     end
     checkFileList(concatArrays(new_files, changed_files), item)
+    removeEmptyDirs(item)
     return new_files
 end