Resolve variables in hrefs.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20340

(cherry picked from commit f4a5404e0a)

common/plotters/PDF_plotter.cpp

@@ -1304,8 +1304,8 @@ bool PDF_PLOTTER::EndPlot()
 
     for( const auto& [ linkHandle, linkPair ] : m_hyperlinkHandles )
     {
-        const BOX2D&    box = linkPair.first;
-        const wxString& url = linkPair.second;
+        BOX2D    box = linkPair.first;
+        wxString url = linkPair.second;
 
         startPdfObject( linkHandle );
 
@@ -1345,6 +1345,9 @@ bool PDF_PLOTTER::EndPlot()
         }
         else
         {
+            if( m_project )
+                url = ResolveUriByEnvVars( url, m_project );
+
             fprintf( m_outputFile,
                      "/A << /Type /Action /S /URI /URI %s >>\n"
                      ">>\n",