[libcalamares] Expand API to allow clearing out the filesystem use

src/libcalamares/partition/Global.cpp

@@ -45,3 +45,12 @@ CalamaresUtils::Partition::useFilesystemGS( Calamares::GlobalStorage* gs, const
         gs->insert( fsUse_key, existingMap );
     }
 }
+
+void
+CalamaresUtils::Partition::clearFilesystemGS( Calamares::GlobalStorage* gs )
+{
+    if ( gs )
+    {
+        gs->remove( fsUse_key );
+    }
+}

src/libcalamares/partition/Global.h

@@ -52,6 +52,12 @@ void DLLEXPORT useFilesystemGS( Calamares::GlobalStorage* gs, const QString& fil
  */
 bool DLLEXPORT isFilesystemUsedGS( const Calamares::GlobalStorage* gs, const QString& filesystemType );
 
+/** @brief Clears the usage data for filesystems
+ *
+ * This removes the internal key *filesystem_use*.
+ */
+void DLLEXPORT clearFilesystemGS( Calamares::GlobalStorage* gs );
+
 /** @brief Convenience function for using "the" Global Storage
  *
  * @see useFilesystemGS(const QString&, bool)