[patch] only check for hg without --with-openjdk-src-zip

[Matthias Klose]

Lillian Angel schrieb:
> Matthias Klose wrote:
>> We don't need Mercurial when building from the src.zip file.
>>
>>   Matthias
>>   
> I am not sure if that is a good idea. You can still specify
> --with-openjdk-src-zip but use the "dist-openjdk" target which requires hg.

I think it is. I do not want to add random build dependencies to a package if I
don't need them (plus I would have to package the forest extension as well).
The"dist-openjdk" target is not used by default, IMO an error message would be
more appropriate.