ci: re-enable testing of ./v -freestanding run vlib/os/bare/bare_example_linux.v on ubuntu

vlib/builtin/linux_bare/linux_syscalls.v

@@ -236,7 +236,7 @@ fn sys_read(fd i64, buf &byte, count u64) (i64, Errno) {
 }
 
 // 1 sys_write
-fn sys_write(fd i64, buf &byte, count u64) (i64, Errno) {
+pub fn sys_write(fd i64, buf &byte, count u64) (i64, Errno) {
 	return split_int_errno(sys_call3(1, u64(fd), u64(buf), count))
 }
 

vlib/os/bare/bare_example_linux.v

@@ -4,4 +4,5 @@ fn main() {
 	sys_write(1, s.str, u64(s.len))
 	a := s[0]
 	println('Hello freestanding!')
+	println(a)
 }