Have cmake build llvm-cov.  Patch by arrowdodger.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146071 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index ec06471..75d203e 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -28,6 +28,7 @@
 add_subdirectory(llvm-size)
 
 add_subdirectory(llvm-ld)
+add_subdirectory(llvm-cov)
 add_subdirectory(llvm-prof)
 add_subdirectory(llvm-link)
 add_subdirectory(lli)