Add support for option `--android-runtime-root` to ART run-test scripts.

Also have testrunner.py honor `ART_TEST_ANDROID_RUNTIME_ROOT` and pass
its value via `--android-runtime-root` to art/test/run-test (for
target testing).

These changes are needed for the interim period where
- we have code running on the ART Buildbot using
  `ANDROID_RUNTIME_ROOT` to locate files on device (namely ICU code
  looking for ICU .dat prebuilt files); and
- the Runtime APEX is not (yet) available on all environments where
  ART is running (namely the ART Buildbot).

Test: Rely on the ART Buildbot.
Bug: 121117762
Bug: 119293618
Bug: 113373927
Change-Id: I83bbb2442f15ed82eee3369dad1d249227bb3442
diff --git a/test/run-test b/test/run-test
index 83c726e..67bcce7 100755
--- a/test/run-test
+++ b/test/run-test
@@ -386,6 +386,15 @@
         android_root="$1"
         run_args="${run_args} --android-root $1"
         shift
+    elif [ "x$1" = "x--android-runtime-root" ]; then
+        shift
+        if [ "x$1" = "x" ]; then
+            echo "$0 missing argument to --android-runtime-root" 1>&2
+            usage="yes"
+            break
+        fi
+        run_args="${run_args} --android-runtime-root $1"
+        shift
     elif [ "x$1" = "x--update" ]; then
         update_mode="yes"
         shift
@@ -758,6 +767,9 @@
         echo "    --never-clean         Keep the test files even if the test succeeds."
         echo "    --chroot [newroot]    Run with root directory set to newroot."
         echo "    --android-root [path] The path on target for the android root. (/system by default)."
+        echo "    --android-runtime-root [path]"
+        echo "                          The path on target for the Android Runtime root."
+        echo "                          (/apex/com.android.runtime by default)."
         echo "    --dex2oat-swap        Use a dex2oat swap file."
         echo "    --instruction-set-features [string]"
         echo "                          Set instruction-set-features for compilation."