haiku: get a cross-compiled compiler working

[jacobly0]

$ zig build -p haiku -Dno-lib -Dtarget=x86_64-haiku -Dcpu=x86_64_v2 --libc haiku.libc

~> ./zig build-obj hello.zig -target native-haiku
~> cc -o hello hello.o
~> ./hello
Hello, world!

• bootstrap isn't working because single large allocations > 0x3f60e740 bytes fail, even though many allocations of that size succeed.
• zig build-exe isn't working when not linked with llvm.
• -target native-native isn't working because native abi/dynamic linker detection is failing.

Related #17123
Related #18828