vfmt: it can now be used for _platform.v files too, no matter the host os

vlib/os2/os2_darwin.v

@@ -0,0 +1,40 @@
+module os2
+
+#include <fcntl.h>
+struct File {
+	fd int
+}
+
+fn C.perror(charptr)
+
+
+fn C.open(byteptr, int, int) int
+
+
+fn C.write(voidptr, byteptr, int) int
+
+
+fn C.close(int) int
+
+
+pub fn create(path string) ?File {
+	fd := C.open(path.str, C.O_CREAT | C.O_TRUNC | C.O_WRONLY, 0644) // 511
+	if fd == -1 {
+		return error('failed to create "$path":')
+		// os.print_c_errno()
+	}
+	return File{
+		fd}
+}
+
+pub fn (f File) writeln(s string) {
+	ss := s + '\n'
+	ret := C.write(f.fd, ss.str, s.len + 1)
+	if ret == -1 {
+		C.perror('failed to write')
+	}
+}
+
+pub fn (f File) close() {
+	C.close(f.fd)
+}