Check for self.cfg.iterate_options instead of #iters>1

This deals with easyconfigs that have lists with just one element
so they will be iterated: `toy.eb` in tests has
`prebuildopts = "echo \"int main() { return 0; }\" > exts-git.c && ",`
the trailing comma makes that a tuple with one element.

Author: bartoldeman

easybuild/framework/easyblock.py

@@ -2378,7 +2378,7 @@ def handle_iterate_opts(self):
             # handle configure/build/install options that are specified as lists (+ perhaps builddependencies)
             # set first element to be used, keep track of list in self.iter_opts
             # only needs to be done during first iteration, since after that the options won't be lists anymore
-            if self.iter_idx == 0 and self.det_iter_cnt() > 1:
+            if self.iter_idx == 0 and self.cfg.iterate_options:
                 # keep track of list, supply first element as first option to handle
                 for opt in ITERATE_OPTIONS:
                     self.iter_opts[opt] = self.cfg[opt]  # copy
@@ -2391,6 +2391,9 @@ def handle_iterate_opts(self):
             # pop first element from all iterative easyconfig parameters as next value to use
             for opt, value in self.iter_opts.items():
                 if opt not in self.cfg.iterate_options:
+                    # Use original value even for options that were specified as strings so don't change
+                    # (ie. elements in ITERATE_OPTIONS but not in self.cfg.iterate_options), so they
+                    # are restored after an easyblock such as CMakeMake changes them
                     self.cfg[opt] = value
                 elif len(value) > self.iter_idx:
                     self.cfg[opt] = value[self.iter_idx]