Sorry for the short, ambiguous description.
I meant, after step 2, I have a usable image with 3G file system, and is able to boot the Galileo from the image on a micro SD card.
And after step 4, I have all the libraries, headers needed to run my application binaries.
In step 5, I use sct to move everything (libraries, headers, applications) to Galileo.
basically libcryptopp's makefile appends
environment-setup-i586-poky-linux-uclibc. After deleting some lines, the compiled libary should work correctly.