[build] Require JDK 11 as our minimum. (#1123)

Context: 738de61

When multiple JDK's are found, a JDK 8 might be chosen.

Specify `JdkInfo.MinimumJdkVersion="11"` to ensure we use
JDK-11 or newer.

Author: jpobst

build-tools/scripts/Prepare.targets

@@ -20,6 +20,7 @@
     <JdkInfo
         JdksRoot="$(JdksRoot)"
         MakeFragmentFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\JdkInfo.mk"
+        MinimumJdkVersion="11"
         MaximumJdkVersion="$(_MaxJdk)"
         DotnetToolPath="$(DotnetToolPath)"
         PropertyFile="$(_TopDir)\bin\Build$(Configuration)\JdkInfo.props">