Changes to support ARM cross compilation.

Added a flag to allow verbose make-kpkg and a flag to specify the
cross compile tools.

Changed the default output_root to use ARCH in the path.

Modified determination of ARCH and changed ARCH=arm to the more correct
ARCH=armel. Also set KPKG_ARCH=arm for compliance with kernel makefile.

Disabled the setarch command when it fails and instead alias uname to
echo ARCH.

A call to compile for arm will look like:
./build_kernel.sh --config=path/to/config --cross_compile=arm-linux-gnueabi- \
[--verbose]

Review URL: http://codereview.chromium.org/501019

build_kernel.sh

@@ -21,17 +21,23 @@ SRC_ROOT=$(dirname $(readlink -f $(dirname "$0")))
 KERNEL_DIR="$SRC_ROOT/third_party/kernel"
 DEFAULT_KCONFIG="${KERNEL_DIR}/files/chromeos/config/chromeos-intel-menlow"
 
+CROSS_COMPILE_FLAG=""
+VERBOSE_FLAG=""
+
 # Flags
 DEFAULT_BUILD_ROOT=${BUILD_ROOT:-"${SRC_ROOT}/build"}
 DEFINE_string config "${DEFAULT_KCONFIG}"                              \
   "The kernel configuration file to use."
 DEFINE_integer revision 002                                            \
   "The package revision to use"
-DEFINE_string output_root "${DEFAULT_BUILD_ROOT}/x86/local_packages"   \
+DEFINE_string output_root ""   \
   "Directory in which to place the resulting .deb package"
 DEFINE_string build_root "$DEFAULT_BUILD_ROOT"                         \
   "Root of build output"
-FLAGS_HELP="Usage: $0 [flags]"
+DEFINE_string cross_compile "" \
+  "Prefix for cross compile build tools"
+DEFINE_boolean verbose $FLAGS_FALSE "Print debugging information in addtion to normal processing."
+FLAGS_HELP="Usage: $0 [flags]" 
 
 # Parse command line
 FLAGS "$@" || exit 1
@@ -40,10 +46,6 @@ eval set -- "${FLAGS_ARGV}"
 # Die on any errors.
 set -e
 
-# TODO: We detect the ARCH below. We can sed the FLAGS_output_root to replace
-# an ARCH placeholder with the proper architecture rather than assuming x86.
-mkdir -p "$FLAGS_output_root"
-
 # Get kernel package configuration from repo.
 # TODO: Find a workaround for needing sudo for this. Maybe create a symlink
 # to /tmp/kernel-pkg.conf when setting up the chroot env?
@@ -52,23 +54,33 @@ sudo cp "$KERNEL_DIR"/package/kernel-pkg.conf /etc/kernel-pkg.conf
 # Parse kernel config file for target architecture information. This is needed
 # to determine the full package name and also to setup the environment for
 # kernel build scripts which use "uname -m" to autodetect architecture.
-KCONFIG="$FLAGS_config"
+KCONFIG=`readlink -f "$FLAGS_config"`
 if [ ! -f "$KCONFIG" ]; then
     KCONFIG="$KERNEL_DIR"/files/chromeos/config/"$KCONFIG"
 fi
-if [ -n $(grep 'CONFIG_X86=y' "$KCONFIG") ]
+if [  $(grep 'CONFIG_X86=y' "$KCONFIG") ]
 then
     ARCH="i386"
-elif [ -n $(grep 'CONFIG_X86_64=y' "$KCONFIG") ]
+elif [ $(grep 'CONFIG_X86_64=y' "$KCONFIG") ]
 then
     ARCH="x86_64"
-elif [ -n $(grep 'CONFIG_ARM=y' "$KCONFIG") ]
+elif [ $(grep 'CONFIG_ARM=y' "$KCONFIG") ]
 then
-    ARCH="arm"
+    ARCH="armel"
+    KPKG_ARCH=arm
 else
     exit 1
 fi
 
+if [ ! $FLAGS_output_root ]
+then
+    FLAGS_output_root="${DEFAULT_BUILD_ROOT}/${ARCH}/local_packages" 
+fi
+
+# TODO: We detect the ARCH below. We can sed the FLAGS_output_root to replace
+# an ARCH placeholder with the proper architecture rather than assuming x86.
+mkdir -p "$FLAGS_output_root"
+
 # Parse the config file for a line with "version" in it (in the header)
 # and remove any leading text before the major number of the kernel version
 FULLVERSION=$(sed -e '/version/ !d' -e 's/^[^0-9]*//' $KCONFIG)
@@ -129,12 +141,38 @@ else
     CONCURRENCY_LEVEL=$(($(cat /proc/cpuinfo | grep "processor" | wc -l) * 2))
 fi
 
+# Setup the cross-compilation environment, if necessary, using the cross_compile
+# Flag from the command line
+if [ $FLAGS_cross_compile ]
+then
+    CROSS_COMPILE_FLAG="--cross-compile $FLAGS_cross_compile"
+fi
+
+if [ $FLAGS_verbose -eq $FLAGS_TRUE ]
+then
+    VERBOSE_FLAG="--verbose"
+fi
+
 # Build the kernel and make package. "setarch" is used so that scripts which
 # detect architecture (like the "oldconfig" rule in kernel Makefile) don't get
 # confused when cross-compiling.
 make-kpkg clean
+
+# Setarch does not support arm, so if we are compiling for arm we need to 
+# make sure that uname -m will return the appropriate architeture. 
+if [ ! -n "$(setarch $ARCH ls)" ]
+then
+    alias uname="echo $ARCH"
+    SETARCH=""
+else
+    SETARCH="setarch $ARCH"
+fi
+
 MAKEFLAGS="CONCURRENCY_LEVEL=$CONCURRENCY_LEVEL" \
-          setarch $ARCH make-kpkg \
+          $SETARCH \
+          make-kpkg \
+          $VERBOSE_FLAG \
+          $CROSS_COMPILE_FLAG \
           --append-to-version="-$CHROMEOS_TAG" --revision="$FLAGS_revision" \
           --arch="$ARCH" \
           --rootcmd fakeroot \