Fix ART buildbots to use jdk8 prebuilts

Test: Manual
Bug: 63902894
Change-Id: I139e613df6efcabd5ca667d6d569cc7577e57355
diff --git a/test/testrunner/env.py b/test/testrunner/env.py
index 6596ff4..b996b04 100644
--- a/test/testrunner/env.py
+++ b/test/testrunner/env.py
@@ -32,7 +32,8 @@
                         'TARGET_2ND_ARCH',
                         'TARGET_ARCH',
                         'HOST_PREFER_32_BIT',
-                        'HOST_OUT_EXECUTABLES']
+                        'HOST_OUT_EXECUTABLES',
+                        'ANDROID_JAVA_TOOLCHAIN']
 _DUMP_MANY_VARS = None  # To be set to a dictionary with above list being the keys,
                         # and the build variable being the value.
 def _dump_many_vars(var_name):
@@ -238,3 +239,9 @@
 for tool in ['jack', 'dx', 'smali', 'jasmin', 'dxmerger']:
   binary = tool if tool != 'dxmerger' else 'dexmerger'
   os.environ.setdefault(tool.upper(), HOST_OUT_EXECUTABLES + '/' + binary)
+
+ANDROID_JAVA_TOOLCHAIN = os.path.join(ANDROID_BUILD_TOP,
+                                     _get_build_var('ANDROID_JAVA_TOOLCHAIN'))
+
+# include platform prebuilt java, javac, etc in $PATH.
+os.environ['PATH'] = ANDROID_JAVA_TOOLCHAIN + ':' + os.environ['PATH']
diff --git a/tools/run-jdwp-tests.sh b/tools/run-jdwp-tests.sh
index 225fb39..17c84b4 100755
--- a/tools/run-jdwp-tests.sh
+++ b/tools/run-jdwp-tests.sh
@@ -19,6 +19,11 @@
   exit 1
 fi
 
+if [ -z "$ANDROID_JAVA_TOOLCHAIN" ] ; then
+  source build/envsetup.sh
+  setpaths # include platform prebuilt java, javac, etc in $PATH.
+fi
+
 if [ -z "$ANDROID_HOST_OUT" ] ; then
   ANDROID_HOST_OUT=${OUT_DIR-$ANDROID_BUILD_TOP/out}/host/linux-x86
 fi
diff --git a/tools/run-libcore-tests.sh b/tools/run-libcore-tests.sh
index eef74d2..d549098 100755
--- a/tools/run-libcore-tests.sh
+++ b/tools/run-libcore-tests.sh
@@ -19,6 +19,11 @@
   exit 1
 fi
 
+if [ -z "$ANDROID_JAVA_TOOLCHAIN" ] ; then
+  source build/envsetup.sh
+  setpaths # include platform prebuilt java, javac, etc in $PATH.
+fi
+
 if [ -z "$ANDROID_PRODUCT_OUT" ] ; then
   JAVA_LIBRARIES=out/target/common/obj/JAVA_LIBRARIES
 else