kicad2step: Provide floats separated

Clang++ seems to be in left-field here as it processes a stringstream
1.0X1.0 >> double as a hexadecimal floating point ('X' character) and
throws an error rather than converting 1.0 and stopping when it reaches
a non-numeric character.  This causes errors when exporting step on Mac,
which uses clang++ by default.

Adding spaces to the string is more explicit and doesn't break gcc.  It
will be sufficient until we get rid of kicad2step as an external
utility.

Fixes: lp:1778564
* https://bugs.launchpad.net/kicad/+bug/1778564

(cherry picked from commit e7a9643b37)

pcbnew/dialogs/dialog_export_step.cpp

@@ -298,7 +298,7 @@ void DIALOG_EXPORT_STEP::onExportButton( wxCommandEvent& aEvent )
             }
 
             LOCALE_IO dummy;
-            cmdK2S.Append( wxString::Format( " --user-origin %.6fx%.6f", xOrg, yOrg ) );
+            cmdK2S.Append( wxString::Format( " --user-origin=\"%.6f x %.6f\"", xOrg, yOrg ) );
         }
             break;
 
@@ -308,7 +308,7 @@ void DIALOG_EXPORT_STEP::onExportButton( wxCommandEvent& aEvent )
             xOrg = Iu2Millimeter( bbox.GetCenter().x );
             yOrg = Iu2Millimeter( bbox.GetCenter().y );
             LOCALE_IO dummy;
-            cmdK2S.Append( wxString::Format( " --user-origin %.6fx%.6f", xOrg, yOrg ) );
+            cmdK2S.Append( wxString::Format( " --user-origin=\"%.6f x %.6f\"", xOrg, yOrg ) );
         }
             break;
     }