Note about symbolic linking from "out" to "out_android"

Android instrumentation tests require CHROMIUM_OUT_DIR environment
variable even if "out" is a symbolic link to "out_android".

BUG=NONE

Review URL: https://codereview.chromium.org/1348323004

Cr-Commit-Position: refs/heads/master@{#350067}
diff --git a/docs/android_test_instructions.md b/docs/android_test_instructions.md
index bd100ed5..510002b 100644
--- a/docs/android_test_instructions.md
+++ b/docs/android_test_instructions.md
@@ -123,7 +123,8 @@
 If you build in an output directory other than "out", you may have to tell
 test\_runner.py where you place it. Say you build your android code in
 out\_android, then do `export CHROMIUM_OUT_DIR=out_android` before running the
-command below.
+command below. You have to do this even if your "out" directory is a symlink
+pointing to "out_android".
 
 ## INSTALL\_FAILED\_CONTAINER\_ERROR or INSTALL\_FAILED\_INSUFFICIENT\_STORAGE