Add files installed to root to diff allowlist

system.img is built from both $OUT/system and $OUT/root. As the diff
tool doesn't check $OUT/root, this change temporarily adds two files
under root (adb_keys and init.environ.rc) to allowlist. They will be
removed once the diff tool is fixed.

Bug: 351258461
Test: build
Change-Id: I0f24dcae67c72be5619a86f6f025ec8bcb146084

tools/filelistdiff/allowlist

@@ -78,6 +78,10 @@ lib/libvendorsupport.so
 lib/libwfds.so
 lib/libyuv.so
 
+# b/351258461
+adb_keys
+init.environ.rc
+
 # Known diffs only in the Soong system image
 lib/libhidcommand_jni.so
 lib/libuinputcommand_jni.so