ART: Switch to executable test in run-test

Check that the signal_dumper file exists and is executable.

Bug: 140935398
Test: art/test/testrunner/testrunner.py -t 001-HelloWorld
Change-Id: Ifb30e5c65109617b6b5fa0ce2e40629a0228b963
diff --git a/test/etc/run-test-jar b/test/etc/run-test-jar
index 37210cf..f924386 100755
--- a/test/etc/run-test-jar
+++ b/test/etc/run-test-jar
@@ -1074,10 +1074,10 @@
       fi
 
       # Testing APEX?
-      if adb shell "test -e ${TIMEOUT_DUMPER_PATH_PREFIX}/apex/com.android.art/bin/signal_dumper" ; then
+      if adb shell "test -x ${TIMEOUT_DUMPER_PATH_PREFIX}/apex/com.android.art/bin/signal_dumper" ; then
         TIMEOUT_DUMPER="/apex/com.android.art/bin/signal_dumper"
       # Is it in /system/bin?
-      elif adb shell "test -e ${TIMEOUT_DUMPER_PATH_PREFIX}/system/bin/signal_dumper" ; then
+      elif adb shell "test -x ${TIMEOUT_DUMPER_PATH_PREFIX}/system/bin/signal_dumper" ; then
         TIMEOUT_DUMPER="/system/bin/signal_dumper"
       else
         TIMEOUT_DUMPER=