Fix salesagility#10505 Rebuild and repair can lead to malformed group…

…ed JS files

Make other processes (web users) wait to read the grouped JS files until AFTER they're completely concatenated and written out to disk.

jssource/minify_utils.php

@@ -166,6 +166,9 @@ function ConcatenateFiles($from_path)
 
                     //make sure we have handles to both source and target file
                     if ($trgt_handle) {
+                        // Acquire exclusive lock on the target file.
+                        flock($trgt_handle, LOCK_EX);
+
                         if ($already_minified || isset($excludedFiles[dirname((string) $loc)])) {
                             $buffer = file_get_contents($loc);
                         } else {
@@ -179,6 +182,8 @@ function ConcatenateFiles($from_path)
                             //log error, file did not get appended
                             echo "Error while concatenating file $loc to target file $trgt \n";
                         }
+                        // Release the lock on the target file.
+                        flock($trgt_handle, LOCK_UN);
                         //close file opened.
                         fclose($trgt_handle);
                     }