Revert "libstore: don’t include derivation names in build direct..."

Revert submission 3850

Reason for revert: caused multiple regressions noticed in https://git.lix.systems/lix-project/lix/issues/975 and https://git.lix.systems/lix-project/lix/issues/966 (suspected).

Root cause analysis has not been done yet and this breaks Lix on Darwin on HEAD.

Reverted changes: /q/submissionid:3850

Change-Id: Iee4c3f071238fa58e0e92f0bcc5584ded4a9d71f

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

@@ -446,7 +446,8 @@ try {
 
         /* Create a temporary directory where the build will take
            place. */
-        tmpDirRoot = createTempSubdir(buildDir, std::nullopt, 0700);
+        tmpDirRoot =
+            createTempSubdir(buildDir, "nix-build-" + std::string(drvPath.name()), 0700);
     } catch (SysError & e) {
         /*
          * Fallback to the global tmpdir and create a safe space there
@@ -471,7 +472,9 @@ try {
             settings.buildDir.get(),
             nixBuildsTmp
         );
-        tmpDirRoot = createTempSubdir(nixBuildsTmp, std::nullopt, 0700);
+        tmpDirRoot = createTempSubdir(
+            nixBuildsTmp, "nix-build-" + std::string(drvPath.name()), 0700
+        );
         worker.buildDirOverride = nixBuildsTmp;
     }
     /* The TOCTOU between the previous mkdir call and this open call is unavoidable due to

tests/functional/check.sh

@@ -40,8 +40,8 @@ test_custom_build_dir() {
   nix-build check.nix -A failed --argstr checkBuildId $checkBuildId \
       --no-out-link --keep-failed --option build-dir "$TEST_ROOT/custom-build-dir" 2> $TEST_ROOT/log || status=$?
   [ "$status" = "100" ]
-  [[ 1 == "$(count "$customBuildDir/"*)" ]]
-  local buildDir="$customBuildDir/"*
+  [[ 1 == "$(count "$customBuildDir/nix-build-"*)" ]]
+  local buildDir="$customBuildDir/nix-build-"*
   grep $checkBuildId $buildDir/b/checkBuildId
 }
 test_custom_build_dir