[tlbuild] Inappropriate compiler flag for C++

[Andreas Scherer]

Am 24.02.19 um 02:54 schrieb Paul Vojta:
> | cc1plus: warning: unrecognized command line option ‘-Wno-mismatched-tags’

Closer inspection shows that the problem with the incorrect C++ compiler
flags seems to be contained in 'texk/dvisvgm/'. Most likely it is
introduced by

   texk/dvisvgm/TLpatches/patch-08-makefiles

where AM_CXXFLAGS is prepended by $(WARNING_CFLAGS), thus adding the
non-C++ option '-Wimplicit'. '-Wno-mismatched-tags' comes from the
original sources (version 2.6.2):
https://github.com/mgieseki/dvisvgm/blob/master/src/Makefile.am#L265

Case closed.

Andreas