Ensure correct line breaks in module footer

The different options for the module footers did not have consistent
newline handling:
- modtclfooter & modluafooter did append a line break
- modules_footer (cmdline) did not

Make sure all end with a new line such that they work in combination
especially with the EasyBuild version comment moved to the bottom

easybuild/framework/easyblock.py

@@ -1493,28 +1493,28 @@ def make_module_footer(self):
             footer.append(self.make_module_extra_extensions())
 
         # include modules footer if one is specified
-        if self.modules_footer is not None:
+        if self.modules_footer:
             self.log.debug("Including specified footer into module: '%s'" % self.modules_footer)
             footer.append(self.modules_footer)
 
         if self.cfg['modtclfooter']:
             if isinstance(self.module_generator, ModuleGeneratorTcl):
                 self.log.debug("Including Tcl footer in module: %s", self.cfg['modtclfooter'])
-                footer.extend([self.cfg['modtclfooter'], '\n'])
+                footer.append(self.cfg['modtclfooter'])
             else:
                 self.log.warning("Not including footer in Tcl syntax in non-Tcl module file: %s",
                                  self.cfg['modtclfooter'])
 
         if self.cfg['modluafooter']:
             if isinstance(self.module_generator, ModuleGeneratorLua):
                 self.log.debug("Including Lua footer in module: %s", self.cfg['modluafooter'])
-                footer.extend([self.cfg['modluafooter'], '\n'])
+                footer.append(self.cfg['modluafooter'])
             else:
                 self.log.warning("Not including footer in Lua syntax in non-Lua module file: %s",
                                  self.cfg['modluafooter'])
 
         footer.append(self.module_generator.comment("Built with EasyBuild version %s" % VERBOSE_VERSION))
-        return ''.join(footer)
+        return '\n'.join(footer)
 
     def make_module_extend_modpath(self):
         """