This will be entirely based on Cross Linux From Scratch with some modificantions… So all credits goes to them.
1 2 3 4 5 6 7 flex bison gawk texinfo pkg-config libncurses5 #gdb libpython2.7-dev #gdb
This link can be also use to for cross-compiling QT for pi.
Build and Compile a Cross-Toolchain for Raspberry Pi 3 from source
Cross Linux From Scratch