test/Frontend/filelist.swift: don't fail if a temporary file does not exist

Author: gribozavr

test/Frontend/filelist.swift

@@ -1,4 +1,4 @@
-// RUN: rm %t.txt
+// RUN: rm -rf %t.txt
 // RUN: echo '%S/Inputs/filelist-other.swift' >> %t.txt
 // RUN: echo '%s' >> %t.txt
 // RUN: echo '%S/../Inputs/empty.swift' >> %t.txt
@@ -10,4 +10,4 @@ func test() {
   // compiled.
   // CHECK: error: cannot convert value of type 'Bar' to specified type 'Foo'
   let x: Foo = other()
-}
+}