std.Target: Fix Abi.default() for mips64/mips64el.

This is necessary after:

* 270fbbcd86b02fcd02ad9b818d9de39dfe671754
* 11915ae48e44cfd9d4e5c5823919fb24951e68f9
ddcde20817Alex Rønne Petersen committed on 11/24/2024, 9:11:16 PMparent24ecf45
1 file changedLine totals unavailable