How to link to an older version math library?

I'm about to release a library (.so) to my client. However, my client's platform is a very old debian(9.1 released on 2017). My libray only works with >= glibc-2.27.
I managed to run program by the following tricks

// copy libm-2.27.so from my computer to the old debian
ln -sf ./libm-2.27.so libm.so.6
gcc ./test.c -o ./test -lmylib -L ./ -lm
LD_LIBRARY_PATH=`pwd` ./test

But my client don't accept this solution.
Is it possible to link to an older version of math library ?
For instance, the client gives me the math library and I link my library against it in my computer.

thanks!