I'm using Slackware and I want to install audio/xmms, but I always
get, at the end of the configure step:

Configuration:
  Install path:               /usr/pkg
  Build OSS plugin:           yes
  Build esd plugin:           no
  Build Solaris plugin:       no
  Build BSD Sun plugin:       no
  Build ALSA plugin:          no
  Build mikmod plugin:        yes
  Build Ogg Vorbis plugin:    yes
  Build OpenGL plugins:       yes
  Pthread flag:               -lpthread
  Use one plugin dir:         no
  Allow user plugin dir:      yes

Since I use ALSA, I would like this plugin to be built. When I check
out the config.log file, I find following related lines:

configure:15874: checking for ALSA CFLAGS
configure:15880: result:
configure:15883: checking for ALSA LDFLAGS
configure:15896: result:  -lasound -lm -ldl -lpthread
configure:15900: checking for libasound headers version >= 0.9.0
configure:15969: gcc -c -O2 -march=athlon-xp -I/usr/pkg/include
-DGLX_GLXEXT_LEGACY -I/usr/include -I/usr/pkg/include/freetype2
-DHAVE_ICONV_OPEN=1 -I/usr/pkg/include -DGLX_GLXEXT_LEGACY
-I/usr/include -I/usr/pkg/include/freetype2 conftest.c >&5
configure:16002:28: alsa/asoundlib.h: No such file or directory
configure:16030:12: #error not present

However, the file /usr/pkg/include/alsa/asoundlib.h does exist.