Ports: Add libuv

We've had a half-arsed port of libuv inside the cmake port, but let's
just port it properly.
Note that this pins a specific commit (which is currently the latest
commit in their default branch).

Ports/libuv/patches/0005-build-Add-SerenityOS-platform-definitions.patch

@@ -0,0 +1,38 @@
+From 1c95dc0ae7732d4389eac1688d3a13ba942f316d Mon Sep 17 00:00:00 2001
+From: Ali Mohammad Pur <ali.mpfard@gmail.com>
+Date: Fri, 9 Jul 2021 05:01:05 +0430
+Subject: [PATCH 5/7] build: Add SerenityOS platform definitions
+
+---
+ CMakeLists.txt | 15 +++++++++++++++
+ 1 file changed, 15 insertions(+)
+
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index de1272a..f30ec26 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -356,6 +356,21 @@ if(CMAKE_SYSTEM_NAME STREQUAL "QNX")
+   list(APPEND uv_libraries socket)
+ endif()
+ 
++if(CMAKE_SYSTEM_NAME STREQUAL "SerenityOS")
++  list(APPEND uv_headers
++    include/uv/posix.h
++  )
++  list(APPEND uv_sources
++    src/unix/posix-hrtime.c
++    src/unix/posix-poll.c
++    src/unix/no-fsevents.c
++    src/unix/no-proctitle.c
++  )
++  list(APPEND uv_libraries
++    dl
++  )
++endif()
++
+ if(APPLE OR CMAKE_SYSTEM_NAME MATCHES "DragonFly|FreeBSD|Linux|NetBSD|OpenBSD")
+   list(APPEND uv_test_libraries util)
+ endif()
+-- 
+2.32.0
+