libreoffice-6.2.2.2 compiling "--with-system-gpgmepp" fails

[John Frankish]

> > Using libreoffice-6.2.2.2, gpgme-1.9.0 and gcc-8.2.0
> > 
> > After copying gpgme headers from include/gpgme++ to include to allow 
> > compiling to progress, make fails with:
> >
> Needs a bit more background - internal gpgme is 1.9.0, too; and e.g. debian is successfully building
> against system-gpgmepp.
> 
> Generally - if you pick non-standard build options, it is usually expected that you fix possible issues
> yourself (and we'd be glad to include any patches for that, of course).
> 
Some more background.

./configure finds the gpgme headers under include/gpgme++:

checking which gpgmepp to use... external
checking gpgme++/gpgmepp_version.h usability... yes
checking gpgme++/gpgmepp_version.h presence... yes
checking for gpgme++/gpgmepp_version.h... yes
checking for progress_callback in -lgpgmepp... yes
checking gpgme.h usability... yes
checking gpgme.h presence... yes
checking for gpgme.h... yes

..but make looks for them under include:

/mnt/sdc8/usr/src/libreoffice-6.2.2.2/comphelper/source/misc/docpasswordhelper.cxx:42:11: fatal error: context.h: No such file or directory
 # include <context.h>
           ^~~~~~~~~~~
compilation terminated.
make[1]: *** [/mnt/sdc8/usr/src/libreoffice-6.2.2.2/solenv/gbuild/LinkTarget.mk:293: /mnt/sdc8/usr/src/libreoffice-6.2.2.2/workdir/CxxObject/comphelper/source/misc/docpasswordhelper.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:286: build] Error 2
Command exited with non-zero status 2

#if HAVE_FEATURE_GPGME
# include <gpgme.h>
# include <context.h>    
# include <data.h>
# include <decryptionresult.h>
#endif