Revert^2 "Remove unused emulator variable"

This reverts commit be416b3155a907d0c3855007795f627a4959e8cc.

Test: Compare output using --dry-run with arguments from buildbots
Change-Id: Idf714390c0dab598abca523b9f15a5773448bf28
diff --git a/tools/run-libcore-tests.sh b/tools/run-libcore-tests.sh
index 7050b0f..726b12d 100755
--- a/tools/run-libcore-tests.sh
+++ b/tools/run-libcore-tests.sh
@@ -93,11 +93,6 @@
   ) | sed -e 's/^  //' >&2 # Strip leading whitespace from heredoc.
 }
 
-emulator="no"
-if [ "$ANDROID_SERIAL" = "emulator-5554" ]; then
-  emulator="yes"
-fi
-
 # Packages that currently work correctly with the expectation files.
 working_packages=("libcore.android.system"
                   "libcore.build"