Rename all_build_flag_declarations.go before adding to it.

Bug: b/370544058
Test: manual, TH
Change-Id: Ia2cbd37458e12f02d5d3193357882cdc8cd3f1d1
diff --git a/aconfig/build_flags/Android.bp b/aconfig/build_flags/Android.bp
index b3c7339..be1b872 100644
--- a/aconfig/build_flags/Android.bp
+++ b/aconfig/build_flags/Android.bp
@@ -13,8 +13,8 @@
         "soong-android",
     ],
     srcs: [
-        "all_build_flag_declarations.go",
         "build_flags.go",
+        "build_flags_singleton.go",
         "declarations.go",
         "init.go",
     ],