amixer problem + solution

To get amixer to work, libasound needs the alsa.conf configuration file. In the default gumstix buildroot for alsa-lib, the configure option --datadir=$(STAGING_DIR)/usr/share must be changed to ie.: --datadir=/usr/share, otherwise it tries to read the alsa.conf from the staging-dir, which is of cause not present on the gumstix. alsa.conf needs to be copied to /usr/share/alsa.conf.