[Windows] Fix test_reachable

Windows doesn't have `/data` or `/usr`. Since Windows does not guarantee
a drive letter actually existing, defer to NSHomeDirectory to give us a
directory which should always exist.

Author: gmittert

TestFoundation/TestURL.swift

@@ -495,6 +495,8 @@ class TestURL : XCTestCase {
     func test_reachable() {
         #if os(Android)
         var url = URL(fileURLWithPath: "/data")
+        #elseif os(Windows)
+        var url = URL(fileURLWithPath: NSHomeDirectory())
         #else
         var url = URL(fileURLWithPath: "/usr")
         #endif
@@ -524,6 +526,8 @@ class TestURL : XCTestCase {
 
         #if os(Android)
         var nsURL = NSURL(fileURLWithPath: "/data")
+        #elseif os(Windows)
+        var nsURL = NSURL(fileURLWithPath: NSHomeDirectory())
         #else
         var nsURL = NSURL(fileURLWithPath: "/usr")
         #endif