[Bug gcov-profile/114115] xz-utils segfaults when built with -fprofile-generate (bad interaction between IFUNC and binding?)

[sjames at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114115

--- Comment #1 from Sam James <sjames at gcc dot gnu.org> ---
One of the xz developers, Jia Tan, has kindly minimised it to not need
BIND_NOW. I've adapted it a bit to cleanup flags and warnings.

I can reproduce it with the following, at least:
```
#!/bin/sh
gcc-14 -O2 -march=znver2 -fvisibility=hidden -fPIC -fprofile-update=atomic
-fprofile-dir=$(pwd) -fprofile-generate=$(pwd) -c test.c -o test.o -Wall
-Wextra
gcc-14 -o libapp.so test.o -shared -Wl,-z,now -fPIC -lgcov
gcc-14 -o app main.c -lgcov -L. -lapp
LD_LIBRARY_PATH=. ./app
```

main.c:
```
#include <stdio.h>

extern int func();

int main(void)
{
    printf( "Hello world %p\n", func);

    return 0;
}
```

test.c:
```
__attribute__((visibility("default")))
void *foo_ifunc2() __attribute__((ifunc("foo_resolver")));


__attribute__((visibility("default")))
void bar(void)
{
}

static int f3()
{
    return 5;
}


__attribute__((visibility("default")))
void (*foo_resolver(void))(void)
{
    f3();
    return bar;
}


__attribute__((optimize("O0")))
__attribute__((visibility("default")))
int func()
{
    foo_ifunc2();
    return 0;
}
```