build: add check for empty openssl-fips flag

Currently, when specifying the --openssl-fips flag without any path
, or an empty path, does not generate an error. If a path is specified
then the following error is generated:

ERROR: FIPS is not supported in this version of Node.js

This commit adds a check so that the error is generated even if the
path is empty.

PR-URL: #25391
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: danbev

configure.py

@@ -1240,7 +1240,7 @@ def without_ssl_error(option):
   if options.openssl_no_asm and options.shared_openssl:
     error('--openssl-no-asm is incompatible with --shared-openssl')
 
-  if options.openssl_fips:
+  if options.openssl_fips or options.openssl_fips == '':
      error('FIPS is not supported in this version of Node.js')
 
   configure_library('openssl', o)