libuv: Comment why we cannot update past 1.44.2

libuv 1.45 and above have higher minimum requirements than we do.
Until we raise ours, we will have to stick with 1.44.2 and backport
any further changes we need.

Utilities/Scripts/update-libuv.bash

@@ -8,6 +8,10 @@ readonly name="libuv"
 readonly ownership="libuv upstream <[email protected]>"
 readonly subtree="Utilities/cmlibuv"
 readonly repo="https://github.com/libuv/libuv.git"
+# We cannot import libuv 1.45 or higher because it has higher
+# minimum system requirements than we do:
+# - It requires C11 atomics from GCC 4.9+.  We support GCC 4.8.
+# - It requires Windows 8, we support Windows 7.
 readonly tag="v1.44.2"
 readonly shortlog=false
 readonly paths="