Changing the call to "--mariadb_config="C:\Program Files\MariaDB 11.8\bin\mariadb_config.pl"
I get the same kind of error : "Specified mysql configuration script 'C:\PROGRA~1\MariaDB 11.8\bin\mariadb_config.pl' doesn't exist.
Please check path/permissions."
Now that I have put the mariadb_config.pl into the 'C:\PROGRA~1\MariaDB 11.8\bin', which is on the path, I have ran the Makefile.pl without the "--mariadb_config" option, and it finds the script by itself. I have, then, another error :

"Checking if libs and header files are available for compiling...
Can't link/include C library 'windows.h', 'winsock.h', 'mysql.h', 'mysqlclient', aborting."

However it finds the parameters from the mariadb_config.pl script :

  cflags         (User's choice) = -IC:\Program Files\MariaDB 11.8\inc
+lude\mysql
  libs           (User's choice) = -LC:\Program Files\MariaDB 11.8\lib
+ -lmysqlclient
  requireembsup  (default      ) = 0
  testauthplugin (default      ) =
  testdb         (User's choice) = test
  testembdatadir (default      ) =
  testemboptions (default      ) =
  testhost       (default      ) =
  testpassword   (default      ) =
  testport       (default      ) =
  testsocket     (default      ) =
  testuser       (User's choice) = perl
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mysql.h is found in directory C:\Program Files\MariaDB 11.8\include\mysql, but not the other 3 required files. I don't where they can be...