Fix grammar-o. Fixes PR13482!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160996 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/Projects.rst b/docs/Projects.rst
index c4be6da..6313288 100644
--- a/docs/Projects.rst
+++ b/docs/Projects.rst
@@ -102,7 +102,7 @@
    ``--prefix=<directory>``
        Tell your project where it should get installed.
 
-That's it!  Now all you have to do is type ``gmake`` (or ``make`` if your on a
+That's it!  Now all you have to do is type ``gmake`` (or ``make`` if you're on a
 GNU/Linux system) in the root of your object directory, and your project should
 build.