Turn one unsafe C cast into a safe static_cast

Author: Ericson2314

src/nix/build-remote/build-remote.cc

@@ -322,7 +322,7 @@ static int main_build_remote(int argc, char ** argv)
             //    output ids, which break CA derivations
             if (!drv.inputDrvs.map.empty())
                 drv.inputSrcs = store->parseStorePathSet(inputs);
-            optResult = sshStore->buildDerivation(*drvPath, (const BasicDerivation &) drv);
+            optResult = sshStore->buildDerivation(*drvPath, static_cast<const BasicDerivation &>(drv));
             auto & result = *optResult;
             if (auto * failureP = result.tryGetFailure()) {
                 if (settings.keepFailed) {