Add a scons pnacl finalize step for pnacl_generate_pexe tests.

tests/gdb/nacl.scons

Index: tests/gdb/nacl.scons
diff --git a/tests/gdb/nacl.scons b/tests/gdb/nacl.scons
index 1185e297ea99647cf008037c0b9bb75afd94afff..f45cf800a65f098613e7801e22db8b8fdae0bade 100644
--- a/tests/gdb/nacl.scons
+++ b/tests/gdb/nacl.scons
@@ -29,6 +29,11 @@ env.Append(CCFLAGS=['-O0', '-g', '-fno-omit-frame-pointer'])
 if env.Bit('bitcode'):
   env.Append(LINKFLAGS=['-O0'])
   env.Append(TRANSLATEFLAGS=['-O0'])
+  # This requires preserving nonstable bitcode debug metadata.
+  env.SetBits('nonstable_bitcode')
+
+if env.Bit('skip_nonstable_bitcode'):
+  Return()
 
 test_args = ['--gdb', env['GDB'],
              '--output_dir', env.subst('${TARGET_ROOT}/test_results')]