Add SPDX tags to a few files that were missed earlier.

charts.d/Makefile.am

@@ -1,5 +1,6 @@
 #
 # Copyright (C) 2015 Alon Bar-Lev <alon.barlev@gmail.com>
+# SPDX-License-Identifier: GPL-3.0+
 #
 MAINTAINERCLEANFILES= $(srcdir)/Makefile.in
 

diagrams/Makefile.am

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0+
 MAINTAINERCLEANFILES= $(srcdir)/Makefile.in
 
 dist_noinst_DATA = \

diagrams/build.sh

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-3.0+
 
 path=$(dirname "$0")
 cd "${path}" || exit 1

src/Makefile.am

@@ -1,5 +1,6 @@
 #
 # Copyright (C) 2015 Alon Bar-Lev <alon.barlev@gmail.com>
+# SPDX-License-Identifier: GPL-3.0+
 #
 MAINTAINERCLEANFILES= $(srcdir)/Makefile.in