Version details: 0.2.36
Distribution/Version: 10.3.9; XCode 1.5

1. Compile and install pkg-config 0.17.2.
2. Compile and install esound.
3. Compile and install libcdio.
4. 'pkg-config --libs esound libcdio'

This gives:
  -Wl,-framework -Wl,CoreFoundation -Wl,-framework -Wl,IOKit -Wl,CoreAudio
-L/sw/lib -lesd -laudiofile -lcdio -lm
instead of:
  -Wl,-framework -Wl,CoreFoundation -Wl,-framework -Wl,IOKit -Wl,-framework
-Wl,CoreAudio -L/sw/lib -lesd -laudiofile -lcdio -lm

The Libs entries in the .pc files contain:

esound.pc:  -L${libdir} -lesd -Wl,-framework -Wl,CoreAudio
libcdio.pc: -L${libdir} -lcdio  -lm  -Wl,-framework -Wl,CoreFoundation
"-Wl,-framework -Wl,IOKit"

pkg-config treats each whitespace-separated word as a separate entity: it
doesn't know -Wl,-framework is the first of a two-word compiler flag, so it 
squeezes out the "duplicate" occurance. That means the second word is passed
bare, which is not correct. This problem occurs whenever esound.pc is used at
the same time as any other .pc that also passes a -Wl,-framework in this manner.

According to the gcc manpage:
  -Wl,option
    Pass option as an option to the linker.  If option contains com-
    mas, it is split into multiple options at the commas.
so esound.pc should contain:
  Libs: -L${libdir} -lesd -Wl,-framework,CoreAudio