Remove repeated words from BuildingLibcxx.rst

Summary: Remove repeated words from docs.

Reviewers: phosek

Reviewed By: phosek

Subscribers: christof

Differential Revision: https://reviews.llvm.org/D60530

llvm-svn: 358147
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: ff79ee144cd62ee4b6eae2f2f809130cda32cadb
diff --git a/docs/BuildingLibcxx.rst b/docs/BuildingLibcxx.rst
index fb22a1d..29a3a2c 100644
--- a/docs/BuildingLibcxx.rst
+++ b/docs/BuildingLibcxx.rst
@@ -201,7 +201,7 @@
 
   **Default**: ``OFF``
 
-  Do not export any symbols from the static libc++ library. This is useful when
+  Do not export any symbols from the static libc++ library.
   This is useful when the static libc++ library is being linked into shared
   libraries that may be used in with other shared libraries that use different
   C++ library. We want to avoid avoid exporting any libc++ symbols in that case.