fix gen_links.sh: don't include source dir as link target

First of all, use one common place to define the gen_links() macro, in
gen_links.sh.inc.

In this new file, add a 'shift' to exclude the $DIR arg from also appearing in
$FILES.

This prevents the following wrong symlinks in the source dirs:

  M3UA_CNL113537/src/src
  MTP3asp_CNL113337/src/src
  SCCP_CNL113341/src/src

Change-Id: Ia8493e77df1ba8723f2c5d2a49816247b0fb55f7
diff --git a/gen_links.sh.inc b/gen_links.sh.inc
new file mode 100644
index 0000000..2fcb9d1
--- /dev/null
+++ b/gen_links.sh.inc
@@ -0,0 +1,12 @@
+#!dont_run_this
+# This file is sourced by */gen_links.sh
+
+gen_links() {
+	DIR=$1
+	shift
+	FILES=$*
+	for f in $FILES; do
+		echo "Linking $f"
+		ln -sf $DIR/$f $f
+	done
+}