The Jargon File (version 4.4.7, 29 Dec 2003):

toolchain


    A collection of tools used to develop for a particular hardware target, or
    to work with a particular data format (thus ?the Crusoe development
    toolchain?, or the ?DocBook toolchain?). Often used in the context of
    building software on one system which will be installed or run on some
    other device; in that case the chain of tools usually consists of such
    items as a particular version of a compiler, libraries, special headers,
    etc. May also be used of text-formatting, page layout, or multimedia tools
    which render from some markup to a variety of production formats. Differs
    from ?toolkit? in that the former implies a collection of semi-independent
    tools with complementary functions, while ?toolchain? implies that each of
    the parts is a serial stage in a rather tightly bound pipeline. Seems to
    have become current in early 1999 and 2000; now common.