The move-constructor precondition assert in OptimizableSymmetryStorage is
malformed: the lambda is captureless ([]), yet odr-uses the member
'symmetries' (needs 'this'), and is never invoked (no trailing () before
the '&& "msg"'). Upstream only compiles because their Release defines
NDEBUG and discards the whole assert(); Gentoo's cmake Release blanks
CMAKE_CXX_FLAGS_RELEASE (no -DNDEBUG, to honour user CFLAGS), so the
assert body is compiled and g++ rejects it.

Fix to match the author's own sibling asserts in the same feature
(core/data/symmetry/CyclicSymmetry.cpp and rigidbody/transform/
TransformStrategy.cpp), which are written '[&]() -> bool { ... }() && "msg"'
— capture by reference, explicit bool return, and invoked. This restores
the intended precondition check. Reported upstream.

--- a/source/rigidbody/parameters/OptimizableSymmetryStorage.cpp
+++ b/source/rigidbody/parameters/OptimizableSymmetryStorage.cpp
@@ -9,13 +9,13 @@ using namespace ausaxs::symmetry;
 using namespace ausaxs::symmetry;

 OptimizableSymmetryStorage::OptimizableSymmetryStorage(SymmetryStorage&& other) : SymmetryStorage(std::move(other)) {
-    assert([] () {
+    assert([&]() -> bool {
         for (const auto& s : symmetries) {
             if (dynamic_cast<const ReferenceSymmetryView*>(s.get()) != nullptr) {
                 return false;
             }
         }
         return true;
-    } && "OptimizableSymmetryStorage::OptimizableSymmetryStorage: Cannot move from a SymmetryStorage that contains ReferenceSymmetryViews.");
+    }() && "OptimizableSymmetryStorage::OptimizableSymmetryStorage: Cannot move from a SymmetryStorage that contains ReferenceSymmetryViews.");
 }
 OptimizableSymmetryStorage::~OptimizableSymmetryStorage() = default;