[PATCH] [compiler-rt] Make the UBSan coverage-levels.cc test be Linux specific

[Alexey Samsonov]

================
Comment at: test/ubsan/TestCases/Misc/Linux/coverage-levels.cc:17
@@ +16,3 @@
+
+// XFAIL: darwin
+
----------------
Remove XFAIL: darwin now.

http://reviews.llvm.org/D8278

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