tests: use different vars for compressing test files

Snappy compress creates temp files, and on windows, its flaky for some reason. Instead of using shadow vars, just use new vars just in case vars are not being properly dropped until var is dropped. Also explicitly dropped cmd var just in case tempfiles are not destroyed until cmd is dropped.

tests/test_joinp.rs

@@ -98,13 +98,14 @@ fn setup(name: &str) -> Workdir {
         .arg("cities.csv")
         .args(["--output", &out_file]);
     wrk.assert_success(&mut cmd);
+    drop(cmd);
 
-    let out_file = wrk.path("places.csv.sz").to_string_lossy().to_string();
-    let mut cmd = wrk.command("snappy");
-    cmd.arg("compress")
+    let out_file2 = wrk.path("places.csv.sz").to_string_lossy().to_string();
+    let mut cmd2 = wrk.command("snappy");
+    cmd2.arg("compress")
         .arg("places.csv")
-        .args(["--output", &out_file]);
-    wrk.assert_success(&mut cmd);
+        .args(["--output", &out_file2]);
+    wrk.assert_success(&mut cmd2);
 
     wrk
 }