Add documentation on the latest build environment extentions to

the README file.

CHANGELOG

@@ -2,6 +2,9 @@
 Changes since U-Boot 1.1.4:
 ======================================================================
 
+* Add documentation on the latest build environment extentions to 
+  the README file.
+
 * Remove dead code (i2o and dma) from cpu/mpc824x/drivers/ directory.
 
 * Fix LOG_DIR directory creation error.

README

@@ -2323,6 +2323,26 @@ images ready for download to / installation on your system:
 - "u-boot" is an image in ELF binary format
 - "u-boot.srec" is in Motorola S-Record format
 
+By default the build is performed locally and the objects are saved
+in the source directory. One of the two methods can be used to change
+this behavior and build U-Boot to some external directory:
+
+1. Add O= to the make command line invocations:
+
+	make O=/tmp/build distclean
+	make O=/tmp/build NAME_config
+	make O=/tmp/build all
+
+2. Set environment variable BUILD_DIR to point to the desired location:
+
+	export BUILD_DIR=/tmp/build
+	make distclean
+	make NAME_config
+	make all
+
+Note that the command line "O=" setting overrides the BUILD_DIR environment
+variable.
+
 
 Please be aware that the Makefiles assume you are using GNU make, so
 for instance on NetBSD you might need to use "gmake" instead of
@@ -2376,6 +2396,22 @@ or to build on a native PowerPC system you can type
 
 	CROSS_COMPILE=' ' MAKEALL
 
+When using the MAKEALL script, the default behaviour is to build U-Boot
+in the source directory. This location can be changed by setting the
+BUILD_DIR environment variable. Also, for each target built, the MAKEALL
+script saves two log files (<target>.ERR and <target>.MAKEALL) in the
+<source dir>/LOG directory. This default location can be changed by
+setting the MAKEALL_LOGDIR environment variable. For example:
+
+	export BUILD_DIR=/tmp/build
+	export MAKEALL_LOGDIR=/tmp/log
+	CROSS_COMPILE=ppc_8xx- MAKEALL
+
+With the above settings build objects are saved in the /tmp/build, log
+files are saved in the /tmp/log and the source tree remains clean during
+the whole build process.
+
+
 See also "U-Boot Porting Guide" below.