Add a note about cygwin


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13927 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index b65bff3..6efb3ce 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -285,7 +285,9 @@
 <p>Note that the LLVM build system does not currently support directories with 
 spaces on them when running on Win32/cygwin.  We strongly recommend running
 LLVM and the C frontend out of a top-level directory without spaces (e.g., 
-<tt>/cygdrive/c/llvm</tt>).</p>
+<tt>/cygdrive/c/llvm</tt>).  Also, make sure to install <b>all</b> of the 
+cygwin packages.  By default, many important tools are not installed that 
+are needed by the LLVM build process or test suite (e.g., /bin/time).</p>
 
 </div>