- fix building out-of-tree;

to test, checkout the source (let's assume /scratch/src/busybox), then
  mkdir /tmp/bb ; cd /tmp/bb
  make top_srcdir=/scratch/src/busybox O="$(pwd)" -f /scratch/src/busybox/Makefile allyesconfig check
- default to O=$(pwd) if no O was specified. Now you can just specify
  the top_srcdir (without O=/somewhere) to create the obj-tree in pwd.
- make "make configtarget buildtarget" work. Previously this didn't
  work due to how HAVE_DOT_CONFIG was evaluated. Two separate steps were
  needed before, e.g. make config ; make busybox.
- remove some unneeded variables from Rules.mak (BB_SRC_DIR from Mr.
  ldoolitt@recycle.lbl) which suggest that the stuff fixed above
  didn't work before.
- move selinux libraries to where they belong (from Makefile to Rules.mak)
- update the docs to mention svn instead of cvs and provide an example
  for building out-of-tree in INSTALL.

Rules.mak

@@ -27,7 +27,7 @@ BUILDTIME := $(shell TZ=UTC date -u "+%Y.%m.%d-%H:%M%z")
 # With a modern GNU make(1) (highly recommended, that's what all the
 # developers use), all of the following configuration values can be
 # overridden at the command line.  For example:
-#   make CROSS=powerpc-linux- BB_SRC_DIR=$HOME/busybox PREFIX=/mnt/app
+#   make CROSS=powerpc-linux- top_srcdir="$HOME/busybox" PREFIX=/mnt/app
 #--------------------------------------------------------
 
 # If you are running a cross compiler, you will want to set 'CROSS'
@@ -60,11 +60,6 @@ LC_ALL:= C
 # For optimization overrides, it's better still to set OPTIMIZATION.
 CFLAGS_EXTRA=$(subst ",, $(strip $(EXTRA_CFLAGS_OPTIONS)))
 
-# If you have a "pristine" source directory, point BB_SRC_DIR to it.
-# Experimental and incomplete; tell the mailing list
-# <busybox@busybox.net> if you do or don't like it so far.
-BB_SRC_DIR=
-
 # To compile vs some other alternative libc, you may need to use/adjust
 # the following lines to meet your needs...
 #
@@ -176,19 +171,20 @@ ifeq ($(strip $(CONFIG_STATIC)),y)
     LDFLAGS += --static
 endif
 
+ifeq ($(strip $(CONFIG_SELINUX)),y)
+    LIBRARIES += -lselinux
+endif
+
 ifeq ($(strip $(PREFIX)),)
     PREFIX:=`pwd`/_install
 endif
 
 # Additional complications due to support for pristine source dir.
 # Include files in the build directory should take precedence over
-# the copy in BB_SRC_DIR, both during the compilation phase and the
+# the copy in top_srcdir, both during the compilation phase and the
 # shell script that finds the list of object files.
 # Work in progress by <ldoolitt@recycle.lbl.gov>.
-#
-ifneq ($(strip $(BB_SRC_DIR)),)
-    VPATH:=$(BB_SRC_DIR)
-endif
+
 
 OBJECTS:=$(APPLET_SOURCES:.c=.o) busybox.o usage.o applets.o
 CFLAGS    += $(CROSS_CFLAGS)