std.zig.system: add OS checks for QEMU in getExternalExecutor()
FreeBSD doesn't support the same number of platforms as Linux, and even then,
only has usermode emulation for a subset of its supported platforms.
NetBSD's usermode emulation support is apparently just broken at the moment.
9e61a64033Alex Rønne Petersen committed on 10/5/2025, 9:33:12 PMparent5969d61