Fix FTBFS with gcc-10

Fixes FTBFS. Patch picked from Debian gnupg1 package, part of Bullseye

[  221s] /usr/bin/ld: ../util/libutil.a(logger.o):./util/../include/mpi.h:49: multiple definition of `mpi_debug_mode'; gpgsplit.o:./tools/../include/mpi.h:49: first defined here
[  221s] /usr/bin/ld: ../util/libutil.a(logger.o):./util/../include/memory.h:97: multiple definition of `memory_stat_debug_mode'; gpgsplit.o:./tools/../include/memory.h:97: first defined here
[  221s] /usr/bin/ld: ../util/libutil.a(logger.o):./util/../include/memory.h:96: multiple definition of `memory_debug_mode'; gpgsplit.o:./tools/../include/memory.h:96: first defined here
[  221s] /usr/bin/ld: ../util/libutil.a(logger.o):./util/../include/iobuf.h:82: multiple definition of `iobuf_debug_mode'; gpgsplit.o:./tools/../include/iobuf.h:82: first defined here
[  221s] /usr/bin/ld: ../util/libutil.a(argparse.o):./util/../include/mpi.h:49: multiple definition of `mpi_debug_mode'; gpgsplit.o:./tools/../include/mpi.h:49: first defined here

Signed-off-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com