Add notes about building kernels

Change-Id: I889967c9a49d1c6040927a17860d0599ce80f993
diff --git a/src/source/sidebar.md b/src/source/sidebar.md
index 362eb04..45189a2 100644
--- a/src/source/sidebar.md
+++ b/src/source/sidebar.md
@@ -4,6 +4,7 @@
 - [Downloading the Source](downloading.html)
 - [Building and Running](building.html)
 - [Building for Devices](building-devices.html)
+- [Building Kernels](building-kernels.html)
 - [Known Issues](known-issues.html)
 
 # Navigating the Source #