Fixed missing dep for "make -j". From Hans T. fix of ISSSort.

[inkdot7]

Fix analog to ISOLDESolenoidalSpectrometer/ISSSort#18

[lpgaff]

I'm holding off on this, because during testing of that in ISSSort, it was giving strange behaviour of the dictionary file names and locations on some systems.

[inkdot7]

@lpgaff Could you elaborate on the issues seen with make -j in ISSSort so we can try to fix those? @hanstt

[lpgaff]

Sorry, just coming back to this. With the changes to the Makefile, it seems that the ROOT dictionaries are compiled with strange names, like the suffix is added twice to the filename. It might be that different versions of make interpret the extra argument in different ways?

[inkdot7]

I could reproduce the error. The issue was that with those two dependencies $(ROOTDICT) would be called twice, and when called for the _rdict.pcm file it generated one with _rdict_rdict.pcm name. It actually makes both the .cc file and then _rdict.pcm file at once, so the needed thing is to tell that the .pcm depends on the .cc.

If it works for you too, I can make a MR for ISSSort as well, unless you beat me to it :-)