fix(tvix): Add newlines to build logs r/1699

.. turns out producing an entire build log on a single line is not
useful.

This does not use `<< std::endl` because we have run into buffering
issues with the implementation of the logs->gRPC sink, but intend to
replace this in the future using a structured sink for BuildEvent
protos rather than a raw stream.

Change-Id: Ia9b05fa804391d389e2ef53ab4436c0ec5cc452e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1828
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

1 files changed, 2 insertions, 2 deletions

diff --git a/third_party/nix/src/libstore/build.cc b/third_party/nix/src/libstore/build.cc
index 60890732e9..83aea3899e 100644
--- a/third_party/nix/src/libstore/build.cc
+++ b/third_party/nix/src/libstore/build.cc
@@ -1473,7 +1473,7 @@ void DerivationGoal::tryToBuild() {
     if (hook) {
       msg += fmt(" on '%s'", machineName);
     }
-    log_sink_ << msg << "[" << drvPath << "]";
+    log_sink_ << absl::StrCat(msg, "[", drvPath, "]\n");
     mcRunningBuilds =
         std::make_unique<MaintainCount<uint64_t>>(worker.runningBuilds);
   };
@@ -3835,7 +3835,7 @@ void DerivationGoal::handleEOF(int /* fd */) {
 void DerivationGoal::flushLine() {
   if (settings.verboseBuild &&
       (settings.printRepeatedBuilds || curRound == 1)) {
-    log_sink_ << currentLogLine;
+    log_sink_ << absl::StrCat(currentLogLine, "\n");
   } else {
     logTail.push_back(currentLogLine);
     if (logTail.size() > settings.logLines) {