Fix common typos in the docs.

llvm-svn: 193632
diff --git a/llvm/docs/HowToBuildOnARM.rst b/llvm/docs/HowToBuildOnARM.rst
index f212acd..b58dfac 100644
--- a/llvm/docs/HowToBuildOnARM.rst
+++ b/llvm/docs/HowToBuildOnARM.rst
@@ -21,7 +21,7 @@
 #. If you are building LLVM/Clang on an ARM board with 1G of memory or less,
    please use ``gold`` rather then GNU ``ld``.
    Building LLVM/Clang with ``--enable-optimized``
-   is prefered since it consumes less memory. Otherwise, the building
+   is preferred since it consumes less memory. Otherwise, the building
    process will very likely fail due to insufficient memory. In any
    case it is probably a good idea to set up a swap partition.