[REBUILD] Fix failures in full-rebuild-from-commits

The bash script pulls and based on commit message titles tells the
build script to do a full rebuild. However, if another build run
is currently running, the build script will just exit. The next
build run now won't see those commits and no full rebuild is done.

Fix by leaving a marker file lying around when we're bailing out due
to another run being active and a full rebuild was requested.

bin/build-project-list.pl

@@ -7,22 +7,20 @@
 use File::Spec::Functions qw/catdir   catfile/;
 use Getopt::Long;
 use Pod::Usage;
+use Mojo::File qw/path/;
 
 use lib qw/lib/;
 use ModulesPerl6::DbBuilder;
 
+use constant FULL_REBUILD_MARK_FILE => 'do-full-rebuild-next-time';
 use constant DB_FILE           => 'modulesperl6.db';
 use constant GITHUB_TOKEN_FILE => 'github-token';
 use constant APP               => 'bin/ModulesPerl6.pl';
 use constant LOGOS_DIR         => catdir  qw/public  content-pics  dist-logos/;
 use constant META_LIST_FILE    => 'https://raw.githubusercontent.com'
                                     . '/perl6/ecosystem/master/META.list';
 
-### This flock exists to allow only one copy of the script to run at a time
-unless ( flock DATA, LOCK_EX | LOCK_NB ) {
-    print "Found duplicate script run. Stopping\n" if $ENV{MODULESPERL6_DEBUG};
-    exit -1;
-}
+exit_if_another_run_is_active();
 
 my $meta_list         = META_LIST_FILE;
 my $github_token_file = GITHUB_TOKEN_FILE;
@@ -56,6 +54,31 @@
     restart_app => $restart_app,
 )->run;
 
+
+sub exit_if_another_run_is_active {
+    my $file = path FULL_REBUILD_MARK_FILE;
+    my $mark = 'ModulesPerl6Org full build marker file';
+
+    ### This flock exists to allow only one copy of the script to run at a time
+    unless ( flock DATA, LOCK_EX | LOCK_NB ) {
+        print "Found duplicate script run. Stopping\n"
+          if $ENV{MODULESPERL6_DEBUG};
+
+        # did previous run wanted us to do a full rebuild, leave a marker
+        # file around so that the next run knows to do the full rebuild
+
+        $file->spurt("$mark; created on " . localtime)
+            if $ENV{FULL_REBUILD} and not -e $file;
+
+        exit -1;
+    }
+
+    if (-e $file and $file->slurp =~ /^\Q$mark\E/) {
+        unlink $file;
+        $ENV{FULL_REBUILD} = 1;
+    }
+}
+
 ### DO NOT REMOVE THE FOLLOWING LINES from __DATA__ ###
 ### This exists to allow only one copy of the script to run at a time
 __DATA__