Add required BY_EXCEPTION_ONLY header comment.

See: http://go/android-license-checking-v2-lsc

Test: m all

Bug: 151953481
Bug: 151177513
Bug: 67772237
Change-Id: Iab2dbbb9d08d26c5d07ba2f6be4baba278fb076b
diff --git a/METADATA b/METADATA
index d0ebd82..4b8bc26 100644
--- a/METADATA
+++ b/METADATA
@@ -1,3 +1,6 @@
+# *** THIS PACKAGE HAS SPECIAL LICENSING CONDITIONS.  PLEASE
+#     CONSULT THE OWNERS AND opensource-licensing@google.com BEFORE
+#     DEPENDING ON IT IN YOUR PROJECT. ***
 name: "MS TPM 2.0 Reference Implementation"
 description: "The official TCG reference implementation of the TPM 2.0 Specification."
 third_party {