libs: modpost failing message for bpf

Describe the bug

When building the bpf probe, I get the following make errors 👇

./include/linux/fortify-string.h:92:17: warning: passing 'unsigned char *' to parameter of type 'const char *' converts between pointers to integer types with different sign [-Wpointer-sign]            
        size_t p_len = __compiletime_strlen(p);                                                                                                                                                           
                       ^~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                            
./include/linux/fortify-string.h:26:29: note: expanded from macro '__compiletime_strlen'                                                                                                                  
                        __ret = __builtin_strlen(__p);          \                                                                                                                                         
                                                 ^~~                                                                                                                                                      
3 warnings generated.                                                                                                                                                                                     
  MODPOST /usr/src/falco-39ae7d40496793cf3d3e7890c9bbdc202263836b/bpf/Module.symvers                                                                                                                      
scripts/mod/modpost: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by scripts/mod/modpost)                                                                                    
scripts/mod/modpost: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by scripts/mod/modpost)
make[2]: *** [scripts/Makefile.modpost:134: /usr/src/falco-39ae7d40496793cf3d3e7890c9bbdc202263836b/bpf/Module.symvers] Error 1
make[1]: *** [Makefile:1749: modules] Error 2
make[1]: Leaving directory '/host/lib/modules/5.18.3-arch1-1/build'

However, the bpf probe is built correctly. 🤔

How to reproduce it

Option # 1 Run make from /usr/src/falco-39ae7d40496793cf3d3e7890c9bbdc202263836b/bpf.

Option # 2

docker run --rm -i -t \                                                                                                                                                                                 
    --privileged \                                                                                                                                                                                        
    -e FALCO_BPF_PROBE="" \                                                                                                                                                                               
    -v /boot:/host/boot:ro \
    -v /lib/modules:/host/lib/modules:ro \
    -v /usr:/host/usr:ro \
    -v /etc:/host/etc:ro \
    falcosecurity/falco-driver-loader:0.32.0

Expected behaviour

No errors.

(perhaps no MODPOST step?)

Screenshots

Environment

Libs version 39ae7d40496793cf3d3e7890c9bbdc202263836b

❯ uname -a
Linux x86 5.18.3-arch1-1 #1 SMP PREEMPT_DYNAMIC Thu, 09 Jun 2022 16:14:10 +0000 x86_64 GNU/Linux
❯ uname -r
5.18.3-arch1-1

Additional context

/cc @Andreagit97 /cc @FedeDP /cc @jasondellaluce