My personal disappointment with autoconf, is that there was no simple file which the package author writes (or even autgenerates) describing what features their package depends on.
There is a file, but its anything but simple and as it (ab)uses m4 and shell script macros that it "knows" exist. It is not reasonable to analyse this file on a foreign OS (e.g. plan9) and work out what might be required to build the package. -Steve