bmc/fs: Ignore missing directories

We shouldn't error out for a missing directory, just ignore it as they
don't have to be present.

Change-Id: I00bd66ca079059753480c73587e0ee41941cd7e6
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/bmc/firmware-handler/test/firmware_json_unittest.cpp b/bmc/firmware-handler/test/firmware_json_unittest.cpp
index 89d4741..9e562c6 100644
--- a/bmc/firmware-handler/test/firmware_json_unittest.cpp
+++ b/bmc/firmware-handler/test/firmware_json_unittest.cpp
@@ -671,5 +671,12 @@
     }
 }
 
+TEST(FirmwareJsonTest, BuildFromMissingDirectory)
+{
+    EXPECT_THAT(
+        FirmwareHandlersBuilder().buildHandlerConfigs("./no-such-directory"),
+        IsEmpty());
+}
+
 } // namespace
 } // namespace ipmi_flash