Revert "Rename ANDROID_PRODUCT_OUT -> PRODUCT_OUT."

Using ANDROID_PRODUCT_OUT is actually the right thing to do.

The reason the bots failed was because I've changed their export to PRODUCT_OUT. I've reverted that change here:
https://chromium-review.googlesource.com/c/chromium/tools/build/+/847512

This reverts commit bf7fbc28a885d50a336eb7a191d24dc15f075360.

Change-Id: Ic67586bc33b8921dd20946238b59fe522fe784dd
diff --git a/test/run-test b/test/run-test
index be8a5a6..75fe15c 100755
--- a/test/run-test
+++ b/test/run-test
@@ -520,10 +520,10 @@
 fi
 
 # Most interesting target architecture variables are Makefile variables, not environment variables.
-# Try to map the suffix64 flag and what we find in ${PRODUCT_OUT}/data/art-test to an architecture name.
+# Try to map the suffix64 flag and what we find in ${ANDROID_PRODUCT_OUT}/data/art-test to an architecture name.
 function guess_target_arch_name() {
-    grep32bit=`ls ${PRODUCT_OUT}/data/art-test | grep -E '^(arm|x86|mips)$'`
-    grep64bit=`ls ${PRODUCT_OUT}/data/art-test | grep -E '^(arm64|x86_64|mips64)$'`
+    grep32bit=`ls ${ANDROID_PRODUCT_OUT}/data/art-test | grep -E '^(arm|x86|mips)$'`
+    grep64bit=`ls ${ANDROID_PRODUCT_OUT}/data/art-test | grep -E '^(arm64|x86_64|mips64)$'`
     if [ "x${suffix64}" = "x64" ]; then
         target_arch_name=${grep64bit}
     else
@@ -562,7 +562,7 @@
 
 if [ "$runtime" = "dalvik" ]; then
     if [ "$target_mode" = "no" ]; then
-        framework="${PRODUCT_OUT}/system/framework"
+        framework="${ANDROID_PRODUCT_OUT}/system/framework"
         bpath="${framework}/core-libart.jar:${framework}/core-oj.jar:${framework}/conscrypt.jar:${framework}/okhttp.jar:${framework}/bouncycastle.jar:${framework}/ext.jar"
         run_args="${run_args} --boot --runtime-option -Xbootclasspath:${bpath}"
     else