libstore: fix non-awaited calls to optimisePath()

LocalStore::optimisePath() was made asynchronous in 38b75b736¹, but we
lost warnings for not awaiting kj::Promise in f68233ec4², since our
capnproto no longer has the [[nodiscard]] patch.

[1]: 38b75b7367
[2]: f68233ec43

Change-Id: I2363396949f40dd43eae08cc76be9ede6b488cf7

lix/libstore/build/local-derivation-goal.cc

@@ -2229,7 +2229,8 @@ try {
                 debug("unreferenced input: '%1%'", worker.store.printStorePath(i));
         }
 
-        localStore.optimisePath(actualPath, NoRepair); // FIXME: combine with scanForReferences()
+        // FIXME: combine with scanForReferences()
+        TRY_AWAIT(localStore.optimisePath(actualPath, NoRepair));
         worker.markContentsGood(newInfo.path);
 
         newInfo.deriver = drvPath;

lix/libstore/local-store.cc

@@ -1166,7 +1166,7 @@ try {
 
             canonicalisePathMetaData(realPath, {});
 
-            optimisePath(realPath, repair); // FIXME: combine with hashPath()
+            TRY_AWAIT(optimisePath(realPath, repair)); // FIXME: combine with hashPath()
 
             TRY_AWAIT(registerValidPath(info));
         }
@@ -1333,7 +1333,7 @@ try {
 
             canonicalisePathMetaData(realPath, {}); // FIXME: merge into restorePath
 
-            optimisePath(realPath, repair);
+            TRY_AWAIT(optimisePath(realPath, repair));
 
             ValidPathInfo info {
                 *this,
@@ -1385,7 +1385,7 @@ try {
             sink << dumpString(s);
             auto narHash = hashString(HashType::SHA256, sink.s);
 
-            optimisePath(realPath, repair);
+            TRY_AWAIT(optimisePath(realPath, repair));
 
             ValidPathInfo info { dstPath, narHash };
             info.narSize = sink.s.size();