$ cat a.c
int w = 100;

int z = 78;

extern int foo()
{
return w + z;
}

extern int main()
{
return foo() + foo() * foo();
}

$ cat b.c
int x = 76;

int y = 87;

#define likely(z) __builtin_expect(!!(z), 1)

extern int __wrap_foo()
{
if (likely(x)) {
return __real_foo();
}
int i,s;
for (i = 0; i < 10000; i++)
s = s + x * y - i;
}

$gcc -flto -fuse-ld=bfd -Wl,--wrap=foo  a.c b.c
/tmp/ccPX4lh2.ltrans0.ltrans.o: in function `__wrap_foo':
<artificial>:(.text+0x6a): undefined reference to `foo'

gcc version: 7.4.0 or gcc trunk
binutils version: 2.33 or binutils trunk

I tried different configurations, this works 
gcc   -flto -fuse-ld=gold -Wl,--wrap=read -O3 a.c b.c
gcc   -flto -fuse-ld=gold -Wl,--wrap=read -O2 a.c b.c
gcc   -flto -fuse-ld=gold -Wl,--wrap=read -O1 a.c b.c


This does not work:

gcc   -flto -fuse-ld=gold -Wl,--wrap=read -O0 a.c b.c
gcc   -flto -fuse-ld=bfd  -Wl,--wrap=read -O3 a.c b.c
gcc   -flto -fuse-ld=bfd  -Wl,--wrap=read -O2 a.c b.c
gcc   -flto -fuse-ld=bfd  -Wl,--wrap=read -O1 a.c b.c
gcc   -flto -fuse-ld=bfd  -Wl,--wrap=read -O0 a.c b.c