RFR: JDK-8202843: langtools ant build fails

[Jan Lahoda]

Hi,

The langtools ant build (used for javac development) fails with:
--
      [exec] 
/usr/local/home/lahvac/src/jdk/jdk10/src/jdk.jshell/share/classes/jdk/internal/jshell/tool/JShellTool.java:3011: 
error: cannot find symbol
      [exec] var url = new URL(filename);
      [exec] ^
      [exec] symbol: class var
      [exec] location: class JShellTool
...
---

This is because the build still uses -source 9 -target 9, while the code 
already uses type inference. We could update the setting to -source 10 
-target 10, but I am not sure we need it - can we just use the default? 
This is not an official build, so some small differences from the 
official build are acceptable I think.

Proposed webrev:
http://cr.openjdk.java.net/~jlahoda/8202843/webrev.00/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8202843

Thanks,
     Jan