JetBrains OpenJDK 11 detection (#82)

Context: https://bintray.com/jetbrains/intellij-jdk/openjdk11-osx-x64
OpenJDK 11 from JetBrains does not have the `jre` directory which, so
far, has been required by the `JdkInfo` class. Instead, there's just
the `lib` directory which should be searched for the JVM libraries
instead of `jre`.
Modify `JdkInfo` so that it first checks the `jre` directory and,
failing to find it, looks for the `lib` directory in the OpenJDK
installation root.
These changes allow Xamarin.Android.Tools tp detect
JetBrains OpenJDK 11 properly.

Author: grendello

src/Xamarin.Android.Tools.AndroidSdk/JdkInfo.cs

@@ -13,6 +13,10 @@
 namespaceXamarin.Android.Tools
 {
 publicclassJdkInfo{
+staticreadonlystring[]JdkLibraryTopDirs={
+"jre",
+"lib",
+};
 
 publicstringHomePath{get;}
 
@@ -52,9 +56,23 @@ public JdkInfo (string homePath)
 JarPath=ProcessUtils.FindExecutablesInDirectory(binPath,"jar").FirstOrDefault();
 JavaPath=ProcessUtils.FindExecutablesInDirectory(binPath,"java").FirstOrDefault();
 JavacPath=ProcessUtils.FindExecutablesInDirectory(binPath,"javac").FirstOrDefault();
+
+stringtopDir=null;
+foreach(stringdirinJdkLibraryTopDirs){
+topDir=Path.Combine(HomePath,dir);
+if(!Directory.Exists(topDir)){
+topDir=null;
+continue;
+}
+break;
+}
+
+if(String.IsNullOrEmpty(topDir))
+topDir=Path.Combine(HomePath,JdkLibraryTopDirs[0]);
+
 JdkJvmPath=OS.IsMac
-?FindLibrariesInDirectory(Path.Combine(HomePath,"jre"),"jli").FirstOrDefault()
-:FindLibrariesInDirectory(Path.Combine(HomePath,"jre"),"jvm").FirstOrDefault();
+?FindLibrariesInDirectory(topDir,"jli").FirstOrDefault()
+:FindLibrariesInDirectory(topDir,"jvm").FirstOrDefault();
 
 ValidateFile("jar",JarPath);
 ValidateFile("java",JavaPath);