refactor(tvix): Remove default buildMode arguments from libstore

These were not used anyway, and *may* have been causing a weird series
of problems leading to things sometimes aborting. Or maybe it has
nothing to do with it - the only correlation we've found is from
disassembling the output of a core dump. Regardless, this feels
stylistically like a good idea.

Change-Id: I288b50945e74ea90c118a21767fa4387c9f47f7d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1921
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>

third_party/nix/src/libstore/build.cc

@@ -284,11 +284,11 @@ class Worker {
   /* Make a goal (with caching). */
   GoalPtr makeDerivationGoal(std::ostream& log_sink, const Path& drvPath,
                              const StringSet& wantedOutputs,
-                             BuildMode buildMode = bmNormal);
+                             BuildMode buildMode);
 
   std::shared_ptr<DerivationGoal> makeBasicDerivationGoal(
       std::ostream& log_sink, const Path& drvPath, const BasicDerivation& drv,
-      BuildMode buildMode = bmNormal);
+      BuildMode buildMode);
 
   GoalPtr makeSubstitutionGoal(std::ostream& log_sink, const Path& storePath,
                                RepairFlag repair = NoRepair);
@@ -888,10 +888,10 @@ class DerivationGoal : public Goal {
 
  public:
   DerivationGoal(Worker& worker, std::ostream& log_sink, const Path& drvPath,
-                 StringSet wantedOutputs, BuildMode buildMode = bmNormal);
+                 StringSet wantedOutputs, BuildMode buildMode);
 
   DerivationGoal(Worker& worker, std::ostream& log_sink, const Path& drvPath,
-                 const BasicDerivation& drv, BuildMode buildMode = bmNormal);
+                 const BasicDerivation& drv, BuildMode buildMode);
 
   ~DerivationGoal() override;