resolveLookupPathPath(): Fix caching of negative lookups

This avoids spamming in case the missing search path entry does not
exist (#12480).

(cherry picked from commit df08e1e)

# Conflicts:
#	src/libexpr/eval.cc

Author: edolstra

src/libexpr/eval.cc

@@ -3084,8 +3084,16 @@ std::optional<std::string> EvalState::resolveLookupPathPath(const LookupPath::Pa
     auto i = lookupPathResolved.find(value);
     if (i != lookupPathResolved.end()) return i->second;
 
+<<<<<<< HEAD
     auto finish = [&](std::string res) {
         debug("resolved search path element '%s' to '%s'", value, res);
+=======
+    auto finish = [&](std::optional<SourcePath> res) {
+        if (res)
+            debug("resolved search path element '%s' to '%s'", value, *res);
+        else
+            debug("failed to resolve search path element '%s'", value);
+>>>>>>> df08e1e20 (resolveLookupPathPath(): Fix caching of negative lookups)
         lookupPathResolved.emplace(value, res);
         return res;
     };
@@ -3137,9 +3145,13 @@ std::optional<std::string> EvalState::resolveLookupPathPath(const LookupPath::Pa
         }
     }
 
+<<<<<<< HEAD
     debug("failed to resolve search path element '%s'", value);
     return std::nullopt;
 
+=======
+    return finish(std::nullopt);
+>>>>>>> df08e1e20 (resolveLookupPathPath(): Fix caching of negative lookups)
 }