JLI_Launch has mangled name in jli.dll when building for win32

[Robert Lichtenberger]

I have tried to use the jpackage EA version in combination with the 
win32-build of Java 12 from AdoptOpenJDK.
I was able to build the jpackage EA from the sandbox and built an image 
from the win32 Java 12 build, which then was successfully combined using 
jpackage's --runtime-image option. (BTW I was able to produce working 
packages for win64, mac and linux in that way).

Now when I tried to start the win32 package I get an error message: 
Failed to locate JLI_Launch.

I digged into the jpackage/launcher code and found out that 
runtime/bin/jli.dll is loaded and the function JLI_Launch is called.

But the jli.dll in the win32-build of Java 12 from AdoptOpenJDK has a 
name mangled version  of JLI_Launch in it (_JLI_Launch at 56) which is (I 
think) the reason that the JVM cannot be started.

I've since tried to build Java 12 myself and the effect is reproducible. 
When I build for win64, the jli.dll is correct, when I build 
--with-target-bits=32 from the exact same sources the jli.dll has the 
mangled name.

Other pre-built JDKs (e.g. Liberica JDK) have the same "problem".

Any ideas/hints as to what could cause the problem would be most welcome 
:-).