The JPEG detection does not seem to work reliably

[timj]

OS X builds do not seem to be detecting the JPEG library properly. The test should either determine if the library is installed and not build it, or else build the private Starlink JPEG. This causes problems on OS X where the JPEG can come from multiple different locations and if you do a build with homebrew it won't work with MacPorts. The solution, at least on Mac, may be to trigger the third party build of JPEG regardless of the existence of the library in the system.

[timj]

clang on Yosemite no longer seems to search /usr/local/. This triggers the JPEG build ok but then basic OS X tools start failing because DYLD_LIBRARY_PATH is set (see #1). Either we need to fix all the linking to remove the need for setting the search path or else we need to fix JPEG detection on OS X by simply linking against the ImageIO framework (-framework ImageIO might work but I haven't tested it). This would require a little extra checking in the configure scripts -- I'm actually surprised there aren't pre-canned autoconf macros for OS X framework detection).

[sfgraves]

If I'm fixing up the binaries and .dylibs so we don't have to set a DYLD_LIBRARY_PATH, then I think the best way to solve this issue is to a) always build libjpeg on Mac OSX (at least when distributing) and then b) not set DYLD_LIBRARY_PATH.