jump-targets: Add in board-specific jump targets

This allows the board/ repo to override or otherwise specify new jump targets
specific for that board.

Change-Id: Ia40dedc93e4067ba0d20676df7eba383b5a05082
diff --git a/setup.sh b/setup.sh
index 06fc0e1..bf0d45a 100755
--- a/setup.sh
+++ b/setup.sh
@@ -151,8 +151,11 @@
     JUMP_TARGETS[host]="${HOST_OUT}"
     JUMP_TARGETS[root]="${ROOT_OUT}"
     JUMP_TARGETS[build]="${ROOTDIR}/build"
-    JUMP_TARGETS[kernel]="${ROOTDIR}/linux-${PLATFORM}/"
-    JUMP_TARGETS[uboot]="${ROOTDIR}/uboot-${PLATFORM}/"
+    JUMP_TARGETS[packages]="${ROOTDIR}/packages"
+
+    if [[ -f "${ROOTDIR}/board/jump_targets.sh" ]]; then
+      source "${ROOTDIR}/board/jump_targets.sh"
+    fi
 
     function j
     {