fix find_tool and find_vs_version might returrs incompatible values

On my PC, I have both MSVC 15 and 16 and found out that find_vs_version returns MSVC 16 while find_tool return MSVC 15 linker

src/windows_registry.rs

@@ -80,7 +80,7 @@ pub fn find_tool(target: &str, tool: &str) -> Option<Tool> {
     // environment variables like `LIB`, `INCLUDE`, and `PATH` to ensure that
     // the tool is actually usable.
 
-    return impl_::find_msvc_15(tool, target)
+    return impl_::find_msvc_15plus(tool, target)
         .or_else(|| impl_::find_msvc_14(tool, target))
         .or_else(|| impl_::find_msvc_12(tool, target))
         .or_else(|| impl_::find_msvc_11(tool, target));
@@ -210,7 +210,7 @@ mod impl_ {
 
     #[allow(bare_trait_objects)]
     fn vs16_instances() -> Box<Iterator<Item = PathBuf>> {
-        let instances = if let Some(instances) = vs15_instances() {
+        let instances = if let Some(instances) = vs15plus_instances() {
             instances
         } else {
             return Box::new(iter::empty());
@@ -253,24 +253,36 @@ mod impl_ {
     // Note that much of this logic can be found [online] wrt paths, COM, etc.
     //
     // [online]: https://blogs.msdn.microsoft.com/vcblog/2017/03/06/finding-the-visual-c-compiler-tools-in-visual-studio-2017/
-    fn vs15_instances() -> Option<EnumSetupInstances> {
+    //
+    // Returns MSVC 15+ instances (15, 16 right now), the order should be consider undefined.
+    fn vs15plus_instances() -> Option<EnumSetupInstances> {
         com::initialize().ok()?;
 
         let config = SetupConfiguration::new().ok()?;
         config.enum_all_instances().ok()
     }
 
-    pub fn find_msvc_15(tool: &str, target: &str) -> Option<Tool> {
-        let iter = vs15_instances()?;
+    pub fn find_msvc_15plus(tool: &str, target: &str) -> Option<Tool> {
+        let iter = vs15plus_instances()?;
+        let mut best = None;
         for instance in iter {
             let instance = instance.ok()?;
+            let installation_name = instance.installation_name().ok()?;
             let tool = tool_from_vs15_instance(tool, target, &instance);
-            if tool.is_some() {
-                return tool;
-            }
+            best = match (tool, best) {
+                (Some(tool), None) => Some((installation_name, tool)),
+                (Some(tool), Some((best_installation_name, _))) => {
+                    if best_installation_name < installation_name {
+                        Some((installation_name, tool))
+                    } else {
+                        None
+                    }
+                }
+                _ => None,
+            };
         }
 
-        None
+        best.map(|(_installation_name, tool)| tool)
     }
 
     // While the paths to Visual Studio 2017's devenv and MSBuild could
@@ -281,7 +293,7 @@ mod impl_ {
     //
     // [more reliable]: https://github.com/alexcrichton/cc-rs/pull/331
     fn find_tool_in_vs15_path(tool: &str, target: &str) -> Option<Tool> {
-        let mut path = match vs15_instances() {
+        let mut path = match vs15plus_instances() {
             Some(instances) => instances
                 .filter_map(|instance| {
                     instance