Prevent ro directories from showing lockfile error

(cherry picked from commit d94fd5f979)

common/eda_draw_frame.cpp

@@ -230,7 +230,10 @@ bool EDA_DRAW_FRAME::LockFile( const wxString& aFileName )
 
     m_file_checker = std::make_unique<LOCKFILE>( aFileName );
 
-    return m_file_checker->Locked();
+    // If the file is not valid, or is successfully locked, return true
+    // Invalid lockfiles are the result of bad permissions, so this is
+    // likely not a file that we can override regardless
+    return !m_file_checker->Valid() || m_file_checker->Locked();
 }
 
 

include/lockfile.h

@@ -52,6 +52,13 @@ public:
         fn.SetName( "~" + fn.GetName() );
         fn.SetExt( fn.GetExt() + ".lck" );
 
+        if( !fn.IsFileWritable() )
+        {
+            m_status = true;
+            m_removeOnRelease = false;
+            return;
+        }
+
         m_lockFilename = fn.GetFullPath();
 
         wxFile file;