windows slaves define JDK 5 - 8 variables but do not have those JDKs installed

I ran some experiments on a win10 slave and discovered that while these variables are defined:

echo "%NATIVE_TOOLS%"
echo "%JAVA15%"
echo "%JAVA16%"
echo "%JAVA17%"
echo "%JAVA18%"

-->

"T:\opt\windows\amd64"
"jdk1.5.0_last"
"jdk1.6.0_last"
"jdk1.7.0_last"
"jdk1.8.0_last"

... not all the associated JDKs are actually installed:

FOR %%D IN ( %OPENJDK_1_8_HOME%, %OPENJDK_1_7_HOME%, %JDK1_8_HOME%, %JDK1_7_HOME%, %JDK1_6_HOME%, %JDK1_5_HOME% ) DO ( %%D\bin\java -version ) 

-->

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\openjdk-1.8.0\bin\java -version  ) 
openjdk version "1.8.0_131-1-redhat"
OpenJDK Runtime Environment (build 1.8.0_131-1-redhat-b11)
OpenJDK 64-Bit Server VM (build 25.131-b11, mixed mode)

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\openjdk-1.7.0\bin\java -version  ) 
The system cannot find the path specified.

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\jdk1.8.0_last\bin\java -version  ) 
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\jdk1.7.0_last\bin\java -version  ) 
java version "1.7.0_79"
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\jdk-1.6.0_last\bin\java -version  ) 
The system cannot find the path specified.

C:\mnt\hudson_workspace\workspace-win10>(T:\opt\windows\amd64\jdk-1.5.0_last\bin\java -version  ) 
The system cannot find the path specified.

So... we should consider making sure that at least openjdk-1.7.0 is installed, if not also jdk-1.6 and jdk-1.5, too.