Disable 639-checker-code-sinking in PIC mode.

Test: testrunner.py --host -t 639-checker-code-sinking (skipped)
Bug: 65366606
Change-Id: Ia9ab793b55e6b350d2f4f33d8d077ccb6841703d
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 20cfc34..315476a 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -255,6 +255,11 @@
         "variant": "npictest"
     },
     {
+        "tests": "639-checker-code-sinking",
+        "variant": "pictest",
+        "bug": "http://b/65366606"
+    },
+    {
         "tests": "055-enum-performance",
         "variant": "optimizing | regalloc_gc",
         "description": ["055: Exceeds run time limits due to heap poisoning ",