dsp56k: Add makefile for building from source

Some small amount of postprocessing is required after assembling
bootstrap.asm with a56.  Add a script and makefile for this.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

WHENCE

@@ -372,10 +372,12 @@ Driver: dsp56k - Atari DSP56k support
 
 File: dsp56k/bootstrap.bin
 Source: dsp56k/bootstrap.asm
+Source: dsp56k/Makefile
+Source: dsp56k/concat-bootstrap.pl
 
 Licence: GPLv2 or later
 
-DSP56001 assembler, possibly buildable with a56 from 
+DSP56001 assembler, buildable with a56 from
 http://www.zdomain.com/a56.html
 
 --------------------------------------------------------------------------

dsp56k/Makefile

+bootstrap.bin: bootstrap.asm concat-bootstrap.pl
+	a56 bootstrap.asm >/dev/null
+	perl concat-bootstrap.pl <a56.out >bootstrap.bin
+
+clean:
+	rm -f a56.out bootstrap.bin

dsp56k/concat-bootstrap.pl

+# Postprocessor for dsp56k bootstrap code.
+#
+# Copyright Ben Hutchings 2011.
+#
+# 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 2 of the License, or
+# (at your option) any later version.
+
+use strict;
+use warnings;
+
+my @memory;
+my %symbol;
+
+# Reconstruct memory image and symbol table
+while (<>) {
+    if (/^P ([0-9A-F]{4}) ([0-9A-F]{6})\n/) {
+	$memory[hex($1)] = hex($2);
+    } elsif (/^I ([0-9A-F]{6}) (\w+)\n/) {
+	$symbol{$2} = hex($1);
+    } else {
+	print STDERR "W: did not recognise line $.\n";
+    }
+}
+
+# Concatenate first and second stage.  Second stage is assembled
+# between 'upload' and 'upload_end', but initially loaded at
+# 'real' (end of the first stage).
+for (0 .. ($symbol{real} - 1), $symbol{upload} .. ($symbol{upload_end} - 1)) {
+    my $word = $memory[$_] || 0;
+    print pack('CCC', $word / 65536, ($word / 256) % 256, $word % 256);
+}