So, let see

devkitPro installs things by default in c:\devkitPro, so devkitARM is located in c:\devkitPro\devkitARM, libnds in c:\devkitPro\libnds and MSYS in c:\devkitPro\msys

According with your preferences, you should have a dir tree like this:
Code:
g:\devkitARM\
g:\devkitARM\devkitARM
g:\devkitARM\libnds
g:\devkitARM\msys
As far as I can see, you have some problems with msys too, in fact it does not recognise "tr". Just check if your msys is installed and, in case, if g:\devkitARM\msys\bin is in your PATH

About the build.bat, stated that all is installed, something like that should work:

Code:
@echo off

set path=G:\arm-gba-fpc\bin\arm-gba;g:\lazarus\fpc\2.2.3\bin\i386-win32;%PATH%

make OS_TARGET=gba CPU_TARGET=arm BINUTILSPREFIX=arm-eabi- PP=ppcarm.exe
pause
The devkitPro installer sets a couple of environment variables too (DEVKITARM=/c/devkitPro/devkitARM and DEVKITPRO=/c/devkitPro), so check them both