Add build.header.c

A new module type for creating just a header file. This is useful for e.g.
shared interfaces and so on which are not backed by a library.

scripts/build.header.c/instantiate

@@ -0,0 +1,14 @@
+if [ $# -ne 1 ]
+then
+    print_failure "Wrong number of arguments after module; need HEADER_NAME."
+    echo "HEADER_NAME is the name of the header file."
+    exit 1
+fi
+
+HEADER_NAME=$1
+shift
+
+do_parameter_subst NAME HEADER_NAME
+true
+
+# vim: syntax=sh:expandtab:ts=4:sw=4