options: accept build options in --reconfigure or "meson configure"

Make more of the first-invocation logic apply to subsequent configuration
of the build tree.

This also opens the door for using set_option_maybe_root for the
first invocation.  This is a huge cleanup but also a larger change,
and therefore not something for stable branches.  Leave it for later.

Signed-off-by: Paolo Bonzini <[email protected]>
(cherry picked from commit 1ac86c1)

Author: bonzini

mesonbuild/options.py

@@ -1055,6 +1055,9 @@ def replace(v: str) -> str:
         return changed
 
     def set_option_maybe_root(self, o: OptionKey, new_value: str) -> bool:
+        if not self.is_cross and o.is_for_build():
+            return False
+
         if o in self.options:
             return self.set_option(o, new_value)
         if self.accept_as_pending_option(o):