Add -lm to sanitizer link arguments.

We'll need to intercept a few function in libm.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193644 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index ffaac21..680f89a 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1757,6 +1757,7 @@
   CmdArgs.push_back("-lpthread");
   CmdArgs.push_back("-lrt");
   CmdArgs.push_back("-ldl");
+  CmdArgs.push_back("-lm");
 
   // If possible, use a dynamic symbols file to export the symbols from the
   // runtime library. If we can't do so, use -export-dynamic instead to export