binman: Fix up removal of temporary directories

At present 'make check' leaves some temporary directories around. Part of
this is because we call tools.PrepareOutputDir() twice in some cases,
without calling tools.FinaliseOutputDir() in between.

Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/elf_test.py

@@ -10,6 +10,7 @@ import unittest
 
 import elf
 import test_util
+import tools
 
 binman_dir = os.path.dirname(os.path.realpath(sys.argv[0]))
 
@@ -46,6 +47,10 @@ class FakeSection:
 
 
 class TestElf(unittest.TestCase):
+    @classmethod
+    def setUpClass(self):
+        tools.SetInputDirs(['.'])
+
     def testAllSymbols(self):
         """Test that we can obtain a symbol from the ELF file"""
         fname = os.path.join(binman_dir, 'test', 'u_boot_ucode_ptr')