fix(stdlib): force use of posix path join

[dirkdev98]

Potentially fixes #673

[github-actions]

==== Benchmark result ====

Node.js version: 14
Total benchmarks: 15
          Passed: 15
          Failed: 0
-----------
router - github static path              200000  iterations    8285  ns/op
router - github path params              200000  iterations   10048  ns/op
compas validator simple                 5000000  iterations     269  ns/op
yup validator simple                     100000  iterations   12196  ns/op
fastest-validator validator simple     10000000  iterations     119  ns/op
compas validator nested                 1000000  iterations    1499  ns/op
yup validator nested                      50000  iterations   38423  ns/op
fastest-validator validator nested      2000000  iterations     571  ns/op
logger - strings                         500000  iterations    2721  ns/op
logger - objects                         500000  iterations    3361  ns/op
logger - deep objects                    200000  iterations    6229  ns/op
uuid                                    2000000  iterations     535  ns/op
uuid.isValid                           10000000  iterations     167  ns/op
isNil                                 500000000  iterations       0  ns/op
isPlainObject                          50000000  iterations      20  ns/op

[github-actions]

==== Benchmark result ====

Node.js version: 15
Total benchmarks: 15
          Passed: 15
          Failed: 0
-----------
router - github static path              200000  iterations    6603  ns/op
router - github path params              200000  iterations    8571  ns/op
compas validator simple                 5000000  iterations     222  ns/op
yup validator simple                     100000  iterations   11071  ns/op
fastest-validator validator simple     10000000  iterations     102  ns/op
compas validator nested                 1000000  iterations    1270  ns/op
yup validator nested                      50000  iterations   34339  ns/op
fastest-validator validator nested      2000000  iterations     539  ns/op
logger - strings                         500000  iterations    2626  ns/op
logger - objects                         500000  iterations    3469  ns/op
logger - deep objects                    500000  iterations    4435  ns/op
uuid                                    5000000  iterations     329  ns/op
uuid.isValid                           10000000  iterations     156  ns/op
isNil                                 500000000  iterations       0  ns/op
isPlainObject                         100000000  iterations      17  ns/op

[github-actions]

==== C8 test coverage ====
Statements: 65.95% ( 24850/37679 )
Branches : 65.09% ( 2752 /4228 )
Functions : 66.99% ( 828 /1236 )
Lines : 65.95% ( 24850 /37679 )