Add support for building code for Debian armhf

I think this will work with the Ubuntu-based distribution on the TK1
too.

Change-Id: I62350d2f7a8914fb13c421be427388c6e46c5481
diff --git a/debian/BUILD b/debian/BUILD
index 29c47d7..d3aef1d 100644
--- a/debian/BUILD
+++ b/debian/BUILD
@@ -7,5 +7,6 @@
   deps = cpu_select({
     "roborio": ['@arm-frc-linux-gnueabi-repo//:' + libname],
     "amd64": ['@usr_repo//:' + libname],
+    "armhf": ['@linaro_linux_gcc_4.9_repo//:' + libname],
   }),
 ) for libname in ['libpthread', 'libm', 'libdl', 'librt']]