I have found some interesting infos here: we can use -FDC:\somedir to pass binutils directory to fpc compiler. Another way is is to pass CROSSBINDIR=C:\xbinutilsdir to make, with BINUTILSPREFIX=some-prefix- if our binutils have a prefix.

At this point it can be useful to do a sort of planning. As a starting point we should use the same tools:

[1] Cross Binutils binaries from http://www.gnuarm.org or sources?
[2] FPC binaries 1.9.6 or 1.9.8?
[3] FPC sources 1.9.6 or 1.9.8?

Regarding [1]: binaries for the sake of simplicity, sources for a better gba "targeting"...
[2] and [3]: :?: :?: :?: