Desugared lib dontwarn

This dontwarn is needed in Google3 in some set-up where I believe R8
is applied after either R8 or appReduce.

Change-Id: Ib4d2ca586b69957b7043cf0160878ed52fc96fcf

src/library_desugar/jdk11/desugar_jdk_libs_nio.json

diff --git a/src/library_desugar/jdk11/desugar_jdk_libs_nio.json b/src/library_desugar/jdk11/desugar_jdk_libs_nio.json
index 3295333..dcd5329 100644
--- a/src/library_desugar/jdk11/desugar_jdk_libs_nio.json
+++ b/src/library_desugar/jdk11/desugar_jdk_libs_nio.json
@@ -616,6 +616,7 @@
     "-keepattributes EnclosingMethod",
     "-keepattributes InnerClasses",
     "-dontwarn sun.misc.Unsafe",
-    "-dontwarn wrapper.**"
+    "-dontwarn wrapper.**",
+    "-dontwarn sun.nio.fs.UnixFileSystemProvider"
   ]
 }