configdata.pm: ensure $prefix is defined

Fixes #5471

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5472)

diff --git a/Configure b/Configure
index 3c40a0e..d78066b 100755 (executable)
--- a/Configure
+++ b/Configure
@@ -2444,6 +2444,7 @@ _____
             my $prefix = '';
             $prefix = $config{cross_compile_prefix}
                 if grep { $var eq $_ } @user_crossable;
             my $prefix = '';
             $prefix = $config{cross_compile_prefix}
                 if grep { $var eq $_ } @user_crossable;

+            $prefix //= '';

             print '    ',$var,' ' x (16 - length $var),'= ',
                 (ref $config{$makevars{$var}} eq 'ARRAY'
                  ? join(' ', @{$config{$makevars{$var}}})
             print '    ',$var,' ' x (16 - length $var),'= ',
                 (ref $config{$makevars{$var}} eq 'ARRAY'
                  ? join(' ', @{$config{$makevars{$var}}})