Add new Makefile.PL option --requireembsup

This new Makefile.PL option --requireembsup or the new ENV variable
DBD_MARIADB_REQUIREEMBSUP=1 cause that Makefile.PL will fail if the
Embedded server is not supported by client library.

This allows build scripts to verify that the correct client library
is used for compiling the DBD-MariaDB.

Author: pali

Makefile.PL

@@ -55,6 +55,7 @@ Getopt::Long::GetOptions(
     "testembdatadir:s",
     "testemboptions:s",
     "testauthplugin:s",
+    "requireembsup!",
     "cflags:s",
     "libs:s",
     "mysql_config:s",
@@ -110,6 +111,21 @@ MSG
     }
   }
 
+if (exists $opt->{requireembsup})
+{
+  $source->{'requireembsup'} = "User's choice";
+}
+elsif (defined $ENV{'DBD_MARIADB_REQUIREEMBSUP'})
+{
+  $source->{'requireembsup'} = 'environment';
+  $opt->{'requireembsup'} = !!$ENV{DBD_MARIADB_REQUIREEMBSUP};
+}
+else
+{
+  $source->{'requireembsup'} = 'default';
+  $opt->{'requireembsup'} = 0;
+}
+
 for my $key (qw(testdb testhost testuser testpassword testsocket testport testembdatadir testemboptions testauthplugin cflags libs))
 {
   Configure($opt, $source, $key);
@@ -301,11 +317,11 @@ my $have_embedded = check_lib(
 
 print "Embedded server: " . ($have_embedded ? "supported" : "not supported by client library") . "\n\n";
 
-if (!$have_embedded && $opt->{testhost} eq 'embedded') {
+if (!$have_embedded && ($opt->{testhost} eq 'embedded' || $opt->{requireembsup})) {
   die << "MSG";
 Cannot run test suite against Embedded server (specified via
-option --testhost=embedded) because Embedded server is not
-supported by client library.
+option --testhost=embedded or option --requireembsup) because
+Embedded server is not supported by client library.
 MSG
 }
 
@@ -726,6 +742,7 @@ Possible options are:
   --testauthplugin=<ap>  Use <ap> auth plugin when doing user authentication
                          handshake with server; for older server versions it is
                          needed to pass "mysql_native_password"
+  --requireembsup        Require client library with embedded server support
   --mariadb_config       Synonym for --mysql_config, override it
   --mysql_config=<path>  Specify <path> for mariadb_config or mysql_config script
   --help                 Print this message and exit