Typo fix, no functionality change.

llvm-svn: 216876
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index f18b6fe..b220e95 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -3080,7 +3080,7 @@
     // installation that is *not* within the system root to ensure two things:
     //
     //  1) Any DSOs that are linked in from this tree or from the install path
-    //     above must be preasant on the system root and found via an
+    //     above must be present on the system root and found via an
     //     appropriate rpath.
     //  2) There must not be libraries installed into
     //     <prefix>/<triple>/<libdir> unless they should be preferred over