I struggled a bit before figuring this one out, so in case it might help anyone else, here's how I'm working, not running from an IDE.
In the "battlecode-scaffold-2017-master" folder, create a file, "RUN.bat", which is an ANSI basic .txt type of file.
In this file, add the text, on a single line -
gradlew build & cd "C:\Users\wjb\01_wjb\wjb_java\BattleCode2017\battlecode-scaffold-2017-master\client\" & start "C:\Users\wjb\01_wjb\wjb_java\BattleCode2017\battlecode-scaffold-2017-master\client\" "Battlecode Client.exe"
-with the exception that, rather than the path I use to the "battlecode-scaffold-2017-master" folder, use your own path.
Run the batch file by clicking ( or double-clicking, depending on your preference setup ) on it from within Windows Explorer.
I tried multiple versions of this without success before I found this. The obvious one was to call "gradlew build" and then "start (path)\Battlecode Client.exe", but that didn't work. Nor did chaining those two commands.
"start" is the command to run an executable file.
The ampersand character, & , is used in batch files to put multiple commands on a single line.
It also didn't work to cd ( "change directory" ) and then run the client, without also adding the path.
And the strangest thing was that it required placing the path name in quotes followed by the executable file name within its own quotes. But although I'm old enough to have once used them, I'm by no means anything approaching an expert in batch file composition; but this seems to work ok.