do not add -L/-I flags pointing to the paths given by --prefix.
there's no need and it breaks multilib and cross-compiling.

patch by Mike Frysinger <vapier@gentoo.org>

--- a/autoconf/libFLAC.m4
+++ b/autoconf/libFLAC.m4
@@ -25,24 +25,8 @@ AC_ARG_ENABLE(libFLACtest,
 	      		     [Do not try to compile and run a test libFLAC program]),,
 	      		     [enable_libFLACtest=yes])
 
-  if test "x$libFLAC_libraries" != "x" ; then
-    LIBFLAC_LIBS="-L$libFLAC_libraries"
-  elif test "x$libFLAC_prefix" != "x" ; then
-    LIBFLAC_LIBS="-L$libFLAC_prefix/lib"
-  elif test "x$prefix" != "xNONE" ; then
-    LIBFLAC_LIBS="-L$prefix/lib"
-  fi
-
   LIBFLAC_LIBS="$LIBFLAC_LIBS -lFLAC -lm"
 
-  if test "x$libFLAC_includes" != "x" ; then
-    LIBFLAC_CFLAGS="-I$libFLAC_includes"
-  elif test "x$libFLAC_prefix" != "x" ; then
-    LIBFLAC_CFLAGS="-I$libFLAC_prefix/include"
-  elif test "$prefix" != "xNONE"; then
-    LIBFLAC_CFLAGS="-I$prefix/include"
-  fi
-
   AC_MSG_CHECKING(for libFLAC)
   no_libFLAC=""
 
--- a/autoconf/libOggFLAC.m4
+++ b/autoconf/libOggFLAC.m4
@@ -25,24 +25,8 @@ AC_ARG_ENABLE(libOggFLACtest,
 	      		     [Do not try to compile and run a test libOggFLAC program]),,
 	      [enable_libOggFLACtest=yes])
 
-  if test "x$libOggFLAC_libraries" != "x" ; then
-    LIBOGGFLAC_LIBS="-L$libOggFLAC_libraries"
-  elif test "x$libOggFLAC_prefix" != "x" ; then
-    LIBOGGFLAC_LIBS="-L$libOggFLAC_prefix/lib"
-  elif test "x$prefix" != "xNONE" ; then
-    LIBOGGFLAC_LIBS="-L$prefix/lib"
-  fi
-
   LIBOGGFLAC_LIBS="$LIBOGGFLAC_LIBS -lOggFLAC -lFLAC -lm"
 
-  if test "x$libOggFLAC_includes" != "x" ; then
-    LIBOGGFLAC_CFLAGS="-I$libOggFLAC_includes"
-  elif test "x$libOggFLAC_prefix" != "x" ; then
-    LIBOGGFLAC_CFLAGS="-I$libOggFLAC_prefix/include"
-  elif test "$prefix" != "xNONE"; then
-    LIBOGGFLAC_CFLAGS="-I$prefix/include"
-  fi
-
   AC_MSG_CHECKING(for libOggFLAC)
   no_libOggFLAC=""
 
--- a/autoconf/ogg.m4
+++ b/autoconf/ogg.m4
@@ -26,24 +26,8 @@ AC_ARG_ENABLE(oggtest,
 	      		     [Do not try to compile and run a test Ogg program]),,
 	      [enable_oggtest=yes])
 
-  if test "x$ogg_libraries" != "x" ; then
-    OGG_LIBS="-L$ogg_libraries"
-  elif test "x$ogg_prefix" != "x" ; then
-    OGG_LIBS="-L$ogg_prefix/lib"
-  elif test "x$prefix" != "xNONE" ; then
-    OGG_LIBS="-L$prefix/lib"
-  fi
-
   OGG_LIBS="$OGG_LIBS -logg"
 
-  if test "x$ogg_includes" != "x" ; then
-    OGG_CFLAGS="-I$ogg_includes"
-  elif test "x$ogg_prefix" != "x" ; then
-    OGG_CFLAGS="-I$ogg_prefix/include"
-  elif test "x$prefix" != "xNONE"; then
-    OGG_CFLAGS="-I$prefix/include"
-  fi
-
   AC_MSG_CHECKING(for Ogg)
   no_ogg=""
 
--- a/autoconf/vorbis.m4
+++ b/autoconf/vorbis.m4
@@ -27,27 +27,10 @@ AC_ARG_ENABLE(vorbistest,
 			     [Do not try to compile and run a test Vorbis program]),
 	      , [enable_vorbistest=yes])
 
-  if test "x$vorbis_libraries" != "x" ; then
-    VORBIS_LIBS="-L$vorbis_libraries"
-  elif test "x$vorbis_prefix" != "x" ; then
-    VORBIS_LIBS="-L$vorbis_prefix/lib"
-  elif test "x$prefix" != "xNONE"; then
-    VORBIS_LIBS="-L$prefix/lib"
-  fi
-
   VORBIS_LIBS="$VORBIS_LIBS -lvorbis -lm"
   VORBISFILE_LIBS="-lvorbisfile"
   VORBISENC_LIBS="-lvorbisenc"
 
-  if test "x$vorbis_includes" != "x" ; then
-    VORBIS_CFLAGS="-I$vorbis_includes"
-  elif test "x$vorbis_prefix" != "x" ; then
-    VORBIS_CFLAGS="-I$vorbis_prefix/include"
-  elif test "x$prefix" != "xNONE"; then
-    VORBIS_CFLAGS="-I$prefix/include"
-  fi
-
-
   AC_MSG_CHECKING(for Vorbis)
   no_vorbis=""
 
--- a/configure.in
+++ b/configure.in
@@ -91,21 +91,6 @@ else
   x_config_flag=yes
 fi
 
-# Checking gcc environment
-for i in `echo $LIBRARY_PATH|sed -e 's,:, ,g'`; do
-  LDFLAGS="$LDFLAGS -L${i}"
-done
-for i in `echo $C_INCLUDE_PATH|sed -e 's,:, ,g'`; do
-  CPPFLAGS="$CPPFLAGS -I${i}"
-done
-
-# add $prefix if specified.
-if test "x$prefix" != xNONE -a "x$prefix" != "x$ac_default_prefix" -a "x$prefix" != "x/usr"; then
-  LDFLAGS="-L$prefix/lib $LDFLAGS"
-  SHLDFLAGS="-L$prefix/lib $SHLDFLAGS"
-  CPPFLAGS="-I$prefix/include $CPPFLAGS"
-fi
-
 dnl add --with-includes, --with-libraries
 AC_ARG_WITH(includes,
   AS_HELP_STRING([--with-includes=DIR], [Specify include directories (colon separated)]),