Adapt Build.PL to the absence of FR/Full.pm

Adapt Build.PL to the absence of lib/Number/Phone/FR/Full.pm:
- select author mode if the file is missing
- dist_version_from FR.pm if FR/Full.pm is missing

Build.PL

@@ -5,11 +5,14 @@ use strict;
 use warnings;
 
 use Module::Build;
+use File::Spec;
 
 my $build_module = 'Module::Build';
 
+my $FR_Full_pm = File::Spec->catfile qw(lib Number Phone FR Full.pm);
+
 # Use the extended build only in author environment
-if (-d '.git') {
+if (-d '.git' || ! -f $FR_Full_pm) {
 	print "Building in author mode\n";
 	$build_module = 'inc::Build::Author';
     require inc::Build::Author;
@@ -19,6 +22,8 @@ my $builder = $build_module->new(
 	module_name          => 'Number::Phone::FR',
 	dist_author          => 'Olivier Mengué <dolmen@cpan.org>',
     dist_abstract        => 'Phone number information for France (+33)',
+    # Defaults to FR.pm if FR/Full.pm has not yet been built
+    dist_version_from    => (grep { -e $_ } ('lib/Number/Phone/FR/Full.pm', 'lib/Number/Phone/FR.pm'))[0],
 	license              => 'perl',
 	meta_add             => {
 		resources => {
@@ -33,6 +38,7 @@ my $builder = $build_module->new(
 	},
 	configure_requires => {
 		'Module::Build' => '0.36',
+        'File::Spec' => 0,
 	},
 	build_requires => {
 		'Test::More' => '0.94',