[tools/build] suggest when and how Configure.pl needs to be re-run

tools/build/Makefile.in

@@ -184,7 +184,7 @@ HARNESS_WITH_FUDGE = $(PERL) t/harness --fudge --keep-exit-code --icu=$(HAS_ICU)
 STAGESTATS = @stagestats@
 
 # the default target, TODO: make libraries in 'lib' a variable.
-all: $(PERL6_EXE) $(SETTING)
+all: check-versions $(PERL6_EXE) $(SETTING)
 
 # the install target
 install: all
@@ -362,6 +362,9 @@ help:
 	@echo "  help:              Print this help message."
 	@echo ""
 
+check-versions:
+	@$(PERL) tools/build/check-versions.pl install/bin/nqp
+
 # Makefile: build/Makefile.in build/PARROT_REVISION $(PARROT) Configure.pl
 # 	@echo ""
 # 	@echo "warning: Makefile is out of date... re-run Configure.pl"

tools/build/check-versions.pl

@@ -0,0 +1,41 @@
+#!/usr/bin/perl
+# Copyright (C) 2008-2011, The Perl Foundation.
+
+use strict;
+use warnings;
+use 5.008;
+use lib 'nqp/tools/lib';
+use NQP::Configure qw(slurp cmp_rev read_config);
+
+my @stat_Makefile    = stat 'Makefile';
+my @stat_Makefile_in = stat 'tools/build/Makefile.in';
+
+if ($stat_Makefile[9] < $stat_Makefile_in[9]) { # 9 => modification time
+    die <<EOM
+Makefile is older than tools/build/Makefile.in, run something like
+
+    perl Configure.pl
+
+with --help or options as needed
+
+EOM
+}
+
+my %nqp_config = read_config($ARGV[0]);
+my $nqp_have = $nqp_config{'nqp::version'} || '';
+my ($nqp_want) = split(' ', slurp('tools/build/NQP_REVISION'));
+
+if (!$nqp_have || cmp_rev($nqp_have, $nqp_want) < 0) {
+    my $parrot_option = '--gen-parrot or --with-parrot=path/to/bin/parrot';
+    if (-x 'install/bin/parrot') {
+        $parrot_option = '--with-parrot=install/bin/parrot';
+    }
+    die <<EOM
+NQP $nqp_have is too old ($nqp_want required), run something like
+
+    perl Configure.pl --gen-nqp $parrot_option
+
+EOM
+}
+
+0; # versions are OK