Add known issue about cts-native-xml-generator

Change-Id: Ica0aa6b9be03a79faa19398c3bc69cc8c7d05dc0
diff --git a/src/source/known-issues.md b/src/source/known-issues.md
index 9f5e872..a7dd9fa 100644
--- a/src/source/known-issues.md
+++ b/src/source/known-issues.md
@@ -19,6 +19,17 @@
 Even with our best care, small problems sometimes slip in. This page keeps
 track of the known issues around using the Android source code.
 
+## Missing CTS Native XML Generator ##
+
+**Symptom**: On some builds of IceCreamSandwich and later, the following
+warning is printed early during the build:
+`/bin/bash: line 0: cd: cts/tools/cts-native-xml-generator/src/res: No
+such file or directory`
+
+**Cause**: Some makefile references that path, which doesn't exist.
+
+**Fix**: None. This is a harmless warning.
+
 ## Black Gingerbread Emulator ##
 
 **Symptom**: The emulator built directly from the gingerbread branch