libuv: Build unix tcp support during CMake bootstrap

Using the real `tcp.c` simplifies `cmake-bootstrap.c`, and its
implementation doesn't seem to require any of the platform-specific
definitions.  Also, later it will be needed for `uv_socketpair`.

Utilities/cmlibuv/src/unix/cmake-bootstrap.c

diff --git a/Utilities/cmlibuv/src/unix/cmake-bootstrap.c b/Utilities/cmlibuv/src/unix/cmake-bootstrap.c
index 054775e..77f26d9 100644
--- a/Utilities/cmlibuv/src/unix/cmake-bootstrap.c
+++ b/Utilities/cmlibuv/src/unix/cmake-bootstrap.c
@@ -7,27 +7,10 @@
 void uv__threadpool_cleanup(void) {
 }
 
-int uv__tcp_nodelay(int fd, int on) {
-  errno = EINVAL;
-  return -1;
-}
-
-int uv__tcp_keepalive(int fd, int on, unsigned int delay) {
-  errno = EINVAL;
-  return -1;
-}
-
-int uv_tcp_listen(uv_tcp_t* tcp, int backlog, uv_connection_cb cb) {
-  return -EINVAL;
-}
-
 int uv_udp_open(uv_udp_t* handle, uv_os_sock_t sock) {
   return -EINVAL;
 }
 
-void uv__tcp_close(uv_tcp_t* handle) {
-}
-
 void uv__udp_close(uv_udp_t* handle) {
 }
 

bootstrap

diff --git a/bootstrap b/bootstrap
index c3e1264..61dd3dd 100755
--- a/bootstrap
+++ b/bootstrap
@@ -625,6 +625,7 @@
     src/unix/process.c \
     src/unix/signal.c \
     src/unix/stream.c \
+    src/unix/tcp.c \
     "
 fi