Fixes unit-test-date-helpers failure on win32

[lygstate]

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[ 22/ 76] FAIL (3221226505): build\tests\unittests-es5.1-math\tests\MinSizeRel\unit-test-date-helpers.exe

TEST: Assertion 'ecma_date_make_day (1970, -1, 1) == -2678400000' failed at (main)D:\a\jerryscript\jerryscript\tests\unit-core\test-date-helpers.c:110.

JerryScript-DCO-1.0-Signed-off-by: Yonggang Luo [email protected]

[lygstate]

@zherczeg This can be merged directly