Multiple definition - Rebuild of the Debian archive with clang

"Multiple definition" build failure(s) — clang 12.0.1

Final link is failing because of the extern __inline__ declaration.
Example:

// plop1.c
extern __inline__ void plop() { }

// plop2.c
extern __inline__ void plop() { }

// foo.c
int main () { }

# Makefile
CC=clang
all:
	$(CC) -c plop1.c plop2.c foo.c
	$(CC) -o plop foo.o plop1.o plop2.o

Package	Version	Supposed error message	Full log
baycomepp	0.10-15	fpga.h:168: multiple definition of `writeboundary'; eppfpga.o:/<>/main/./fpga.h:168: first defined here	Log
baycomusb	0.10-14	sysdeps.h:150: multiple definition of `gettimems'; baycomusb.o:/<>/diag/../misc/sysdeps.h:150: first defined here	Log
gnupg1	1.4.23-1.1	ld: ../mpi/libmpi.a(mpi-add.o):./build-deb/mpi/../../include/iobuf.h:81: multiple definition of `iobuf_debug_mode'; mpicalc.o:./build-deb/tools/../../include/iobuf.h:81: first defined here	Log

3 errors