bar.c

#include <stdio.h>
void foo(void);

void bar(void) {
	foo();
	puts("bar\n");
}

foo.c

#include <stdio.h>
void foo(void) {
	puts("foo\n");
}

main

main.c

void bar(void);

int main() {
	bar();
}

Makefile

CFLAGS += -fPIC

all: main

main: main.o foo/libfoo.so bar/libbar.so
	cc -Wl,--copy-dt-needed-entries -Wl,--no-as-needed main.o -o $@ -Wl,-rpath,$(PWD)/bar -Lbar -lbar 

clean:
	rm *.o foo bar -r

foo/libfoo.so: foo.o
	mkdir -p foo
	cc foo.o -o $@ -shared -Wl,-soname,libfoo.so


bar/libbar.so: bar.o foo/libfoo.so
	mkdir -p bar
	cc bar.o -o $@ -shared -Wl,-soname,libbar.so -Lfoo -lfoo -Wl,-rpath,$(PWD)/foo