I don't know how to measure or decide that. I believe I've seen such usage before but I really can't say for sure, or point to an actual example. Sorry.
Here is all I could find: http://www.google.com/codesearch?hl=en&lr=&q=AC_PROG_CC\(.*[%27%22]&sbtn=Search
AC_PROG_CC("$INFORMIXC" cc gcc) # have to take care of INFORMIXC
no arguments, but a quoted variable.
Paolo
