Revert "tests/check.sh: Fix a race"

This reverts commit 0776aa1 because
it's causing a test failure: https://hydra.nixos.org/build/247889890

Author: edolstra

tests/add.sh

@@ -9,7 +9,7 @@ echo $path2
 if test "$path1" != "$path2"; then
     echo "nix-store --add and --add-fixed mismatch"
     exit 1
-fi
+fi    
 
 path3=$(nix-store --add-fixed sha256 ./dummy)
 echo $path3

tests/check.nix

@@ -11,7 +11,7 @@ with import ./config.nix;
   };
 
   hashmismatch = import <nix/fetchurl.nix> {
-    url = "file://" + builtins.getEnv "TMPDIR" + "/dummy";
+    url = "file://" + toString ./dummy;
     sha256 = "0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73";
   };
 

tests/check.sh

@@ -34,9 +34,9 @@ nix-build check.nix -A fetchurl --no-out-link --repair --hashed-mirrors ''
 nix-build check.nix -A hashmismatch --no-out-link --hashed-mirrors '' || status=$?
 [ "$status" = "102" ]
 
-echo -n > $TMPDIR/dummy
+echo -n > ./dummy
 nix-build check.nix -A hashmismatch --no-out-link --hashed-mirrors ''
-echo 'Hello World' > $TMPDIR/dummy
+echo 'Hello World' > ./dummy
 
 nix-build check.nix -A hashmismatch --no-out-link --check --hashed-mirrors '' || status=$?
 [ "$status" = "102" ]