Add the FreeBSD entry stub for a static, libc-free ET_EXEC:
- runtime.start.static.freebsd.pas — the FreeBSD sibling of
runtime.start.static.linux. _start captures %rsp, aligns the stack, and calls
the Pascal _BlaiseStartC, which parses argc/argv/envp off the kernel's initial
stack (same layout as Linux), captures environ, calls main(argc, argv), and
exits via the FreeBSD exit syscall. Deliberately minimal: no TLS/auxv-walk
(a trivial program does no threadvar access) — that lands with the threads
work in Step 4, mirroring how the Linux static start gained TLS.
- runtime.syscall.freebsd.pas — the minimum kernel leaf _start needs: _exit
(SYS_exit = 1), write (SYS_write = 4, aliased from _sys_write), and the
environ global. The full file/process/thread leaf grows here in Step 4. ABI
notes record the FreeBSD differences from Linux: different syscall numbers and
the carry-flag error convention (only relevant for the error-translating
wrappers that arrive in Step 4).
Both units are standalone — nothing in the default Linux build graph uses them,
so the Linux RTL and self-hosting are unaffected; the FreeBSD RTL composition
links them at Step 5.
TLinkerE2ETests.TestLink_FreeBSDStart_StaticExecShape links the _start fixture
with the FreeBSD target and asserts the Strategy-B shape: e_type = ET_EXEC,
entry == _start, no PT_INTERP. (Uses LinkToBytes, not ReadFile — the latter
truncates at the ELF header's first NUL byte.)
Step 3 of docs/freebsd-x86_64-backend-design.adoc. Full suite 3850 green;
FIXPOINT_OK.
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