gjs: add gjs source back

This sets various environment variables we need.

src/libsysprof/sysprof-gjs-source.h

@@ -0,0 +1,35 @@
+/* sysprof-gjs-source.h
+ *
+ * Copyright 2019 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "sysprof-tracefd-source.h"
+
+G_BEGIN_DECLS
+
+#define SYSPROF_TYPE_GJS_SOURCE (sysprof_gjs_source_get_type())
+
+SYSPROF_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (SysprofGjsSource, sysprof_gjs_source, SYSPROF, GJS_SOURCE, SysprofTracefdSource)
+
+SYSPROF_AVAILABLE_IN_ALL
+SysprofSource *sysprof_gjs_source_new (void);
+
+G_END_DECLS