Sort the filenames in Android.mk.

Bug: None
Change-Id: Ifbc50cc5c3bb5132a9c047cd580890918179b375
diff --git a/Android.mk b/Android.mk
index 617737d..c4116e8 100644
--- a/Android.mk
+++ b/Android.mk
@@ -159,10 +159,10 @@
     common/constants.cc \
     common/cpu_limiter.cc \
     common/error_code_utils.cc \
+    common/file_fetcher.cc \
     common/hash_calculator.cc \
     common/http_common.cc \
     common/http_fetcher.cc \
-    common/file_fetcher.cc \
     common/hwid_override.cc \
     common/libcurl_http_fetcher.cc \
     common/multi_range_http_fetcher.cc \