Fix Fem Find Calculix binary (if installed) on Linux

src/Mod/Fem/MechanicalAnalysis.py

@@ -213,8 +213,13 @@ class _JobControlTaskPanel:
         # for the subcomponents, such as additions, subtractions.
         # the categories are shown only if they are not empty.
         self.form=FreeCADGui.PySideUic.loadUi(FreeCAD.getHomePath() + "Mod/Fem/MechanicalAnalysis.ui")
-
-        self.CalculixBinary = FreeCAD.getHomePath() +'bin/ccx.exe'
+        from platform import system
+        if system == 'Linux':
+          self.CalculixBinary = 'ccx'
+        elif  system == 'Windows':
+          self.CalculixBinary = FreeCAD.getHomePath() + 'bin/ccx.exe'
+        else:
+          self.CalculixBinary = 'ccx'
         self.TempDir = FreeCAD.ActiveDocument.TransientDir.replace('\\','/') + '/FemAnl_'+ object.Uid[-4:]
         if not os.path.isdir(self.TempDir):
             os.mkdir(self.TempDir)