This topic was recently discussed here: http://zx-pk.ru/showthread.php?t=21217

For cross-development in Windows there exists a program called "monoscl.exe"; it joins all files in an *.scl file into a single block. This program is a part of "Evo SDK", which can be found here: http://shiru.untergrund.net/files/src/evo_sdcc.zip

For example, this is how I link my boot "Morphine" using Sjasmplus:
Код:
	EMPTYTRD "morphine.trd"
	SAVETRD	"morphine.trd", "boot.B", BasicStart, BasicEnd-BasicStart, 1
	SAVETRD	"morphine.trd", "morphine.C", BinaryFile, FileLength
	SHELLEXEC "cmd /c del morphine.scl"
	SHELLEXEC "_bin\trx2x.exe morphine.trd morphine.scl"
	SHELLEXEC "_bin\monoscl.exe morphine.scl"
	SHELLEXEC "cmd /c del morphine.trd"
	SHELLEXEC "_bin\trx2x.exe morphine.scl morphine.trd"
	SHELLEXEC "cmd /c del morphine.scl"