Thanks you for fast reply.

Can I rebuild glibc build root image ? (Pico Max + nand image )
Because My compiler (FPC : Free Pascal Compiler ) thread model support pthread & glibc only.

I try build image with glibc option. but fail to build.

my test ...

./buildroot.sh buildrootconfig
-> include minicom -> build image ok (exists minicom in result image )
-> tool chain -> external toolchaing c lib (glibc) -> (fail / not found in /usr/lib )

How to include libpthread.so in /usr/lib/libpthread.so ?

Which buildrootconfig option is including ...