Fix Windows FFI build and missing test imports

Message

Guard Unix-only dlopen helpers (try_dlopen, try_linker_script, search_library_path) with #ifndef _WIN32 so the Windows cross-compile via Zig doesn't see undeclared dlopen/RTLD_NOW. The main platform dispatch in ffi_open_library was already guarded.

Add missing (sigil fs) import to cairo, harfbuzz, and freetype tests that use file-exists? — caused unbound variable error in CI.

Changed

 test/test-cairo.sgl | 1 +
 1 file changed, 1 insertion(+)

Diff

test/test-cairo.sglmodified

@@ -3,6 +3,7 @@

(import (sigil core)

(sigil test)

(sigil fs)

(sigil ffi)

(cairo))