Add option to use Ada code in ramstage

If selected, libgnat will be linked into ramstage. And, to support Ada
package intializations, we have to call ramstage_adainit().

Change-Id: I11417db21f16bf3007739a097d63fd592344bce3
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/16944
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/adainit.h

@@ -0,0 +1,35 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#ifndef _ADAINIT_H
+#define _ADAINIT_H
+
+/**
+ * @file adainit.h
+ *
+ * Ada supports some complex constructs that result in code for runtime
+ * initialization. It's also possible to have explicit procedures for
+ * package level initialization (e.g. you can initialize huge arrays in
+ * a loop instead of cluttering the binary).
+ *
+ * When an Ada main() is in charge, GNAT emmits the call to the initia-
+ * lizations automatically. When not, we have to call it explicitly.
+ */
+
+#if IS_ENABLED(CONFIG_RAMSTAGE_ADA)
+void ramstage_adainit(void);
+#else
+static inline void ramstage_adainit(void) {}
+#endif
+
+#endif /* _ADAINIT_H */