Clarify comment and logic

Author: zooba

Modules/getpath.py

@@ -766,10 +766,10 @@ def search_up(prefix, *landmarks, test=isfile):
 # SANITY CHECKS
 # ******************************************************************************
 
-# Warn if the standard library is missing, unless pythonpath_was_set was set, as
-# that skips parts of the stdlib directories calculation — assume the provided
-# pythonpath is correct. This is how subinterpreters initialize the path for eg.
-if not py_setpath and not pythonpath_was_set and not pth:
+# Warn if we did a search for the standard library and couldn't find it. Never
+# show a warning if paths were provided explicitly, since we trust the caller
+# knows what they're doing even if the layout doesn't look "normal".
+if not (py_setpath or pythonpath_was_set or pth):
     home_hint = f"The Python 'home' directory was set to {home!r}, is this correct?"
     if (not stdlib_zip or not isfile(stdlib_zip)) and (not stdlib_dir or not isdir(stdlib_dir)):
         hint = home_hint if home else f'sys.prefix is set to {prefix}, is this correct?'