Add default define of goog.DEBUG=false for optimized builds

[niloc132]

Code compiled by j2cl-maven-plugin gets an extra method defined on globalThis, even when everything else is compiled out:

globalThis.g=function(){};

J2CL's jre.js sets up a special function to prevent certain optimizations: https://github.com/Vertispan/j2cl/blob/aa5f8c2eec98b5314071f96572a9002599754279/jre/java/java/lang/jre.js#L55-L59

// Provide a stub for field preserver to make things work without full
// compilation.
if (!COMPILED || goog.DEBUG) {
  globalThis.$J2CL_PRESERVE$ = function(/** ...* */ e) {};
}

See also https://github.com/Vertispan/j2cl/blob/aa5f8c2eec98b5314071f96572a9002599754279/jre/java/java/lang/externs.js#L22-L25 for the externs that define this method as being external.

Closure-compiler specially looks for this value, guards it to ensure only j2cl code can call it:
https://github.com/Vertispan/closure-compiler/blob/ebf577bd36a6f24a27b71e4498371066a831270d/src/com/google/javascript/jscomp/CheckSideEffects.java#L53-L56

In j2cl-maven-plugin, this code is eventually compiled to

if(!COMPILED||goog.DEBUG)globalThis.$J2CL_PRESERVE$=function(e$jscomp$12){};

Then, defines are inlined:

if(!true||true)globalThis.$J2CL_PRESERVE$=function(e$jscomp$12){};

Which will clearly be kept, though it shouldn't be, according to the comment.

To ensure this is removed, we want goog.DEBUG to be set to false. This is probably a good idea generally, but it might also be possible to remove the goog.DEBUG check and just used COMPILED.