[libudns] use supports expression (microsoft#21448)

ports/libudns/portfile.cmake

@@ -1,5 +1,3 @@
-vcpkg_fail_port_install(MESSAGE "${PORT} currently only supports Linux platform" ON_TARGET "Windows" "OSX") 
-
 vcpkg_from_github(
     OUT_SOURCE_PATH SOURCE_PATH
     REPO ortclib/udns

ports/libudns/vcpkg.json

@@ -1,7 +1,8 @@
 {
   "name": "libudns",
   "version-string": "0.4",
-  "port-version": 3,
+  "port-version": 4,
   "description": "The DNS library, udns, implements thread-safe stub DNS resolver functionality, which may be used both traditional, syncronous way and asyncronously, with application-supplied event loop.",
-  "homepage": "https://github.com/ortclib/udns"
+  "homepage": "https://github.com/ortclib/udns",
+  "supports": "!windows & !osx"
 }

scripts/ci.baseline.txt

@@ -704,14 +704,6 @@ libudis86:arm-uwp=fail
 libudis86:x64-linux=fail
 libudis86:x64-osx=fail
 libudis86:x64-uwp=fail
-libudns:arm64-windows=fail
-libudns:arm-uwp=fail
-libudns:x64-uwp=fail
-libudns:x64-windows=fail
-libudns:x64-windows-static=fail
-libudns:x64-windows-static-md=fail
-libudns:x86-windows=fail
-libudns:x64-osx=fail
 libui:arm-uwp=fail
 libui:x64-linux=fail
 libui:x64-uwp=fail

versions/baseline.json

@@ -3962,7 +3962,7 @@
     },
     "libudns": {
       "baseline": "0.4",
-      "port-version": 3
+      "port-version": 4
     },
     "libui": {
       "baseline": "2018-11-03",

versions/l-/libudns.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "277ba57e6f9840670698c62196ea9b30c74485e0",
+      "version-string": "0.4",
+      "port-version": 4
+    },
     {
       "git-tree": "a05d58223d5adb1f421bbde4a0ac44ce72a3a1c9",
       "version-string": "0.4",