xtensa-build-zephyr: do not clone a second version of sof.git

This script lives in a sof.git/ clone yet it was systematically cloning
a second sof.git/. Besides the obvious confusion and risk of editing the
wrong files, this meant it was not possible to build code that has not
been merged yet! This was a problem for both CI and developers. Fixed by
using symbolic links to ourselves instead.

Note it is _still_ possible to build from another sof.git clone if
desired, however this script will never git re-clone a second sof.git
itself, that second clone has to be created (e.g.: by west) before this
script runs.

When cloning a brand new zephyrproject, use a shallow zephyr clone and
download only the two zephyr modules we actually use. This speeds up
automation considerably and makes it much faster for non-Zephyr
developers to reproduce Zephyr issues. Developers can always git
unshallow and west update once if they want to.

Rename the default west top to "zephyrproject" to not just match the
zephyr documentation but to also avoid creating a double zephyr/zephyr/
directory.

See the new print_usage() for a few more implementation details.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

scripts/xtensa-build-zephyr.sh

@@ -5,9 +5,11 @@
 # stop on most errors
 set -e
 
+SOF_TOP=$(cd "$(dirname "$0")" && cd .. && pwd)
+
 SUPPORTED_PLATFORMS=(apl cnl icl tgl-h)
-# By default use "zephyr" in the current directory
+# Default value, can be overridden on the command line
-ZEPHYR_ROOT=zephyr
+WEST_TOP="${SOF_TOP}"/zephyrproject
 BUILD_JOBS=$(nproc --all)
 RIMAGE_KEY=modules/audio/sof/keys/otc_private_key.pem
 PLATFORMS=()
@@ -31,41 +33,43 @@ platform's _defconfig file.
 usage: $0 [options] platform(s)
 
        -a Build all platforms.
-       -c Clone the complete Zephyr and SOF trees before building.
        -j n Set number of make build jobs. Jobs=#cores by default.
            Infinite when not specified.
        -k Path to a non-default rimage signing key.
-       -p Zephyr root directory.
+       -c recursively clones Zephyr inside sof before building.
+          Incompatible with -p.
+       -p Existing Zephyr project directory. Incompatible with -c.
+          If modules/audio/sof is missing there then a symbolic
+          link pointing to ${SOF_TOP} will be added.
 
 Supported platforms ${SUPPORTED_PLATFORMS[*]}
 
 EOF
 }
 
+# Downloads zephyrproject inside sof/ and create a ../../.. symbolic
+# link back to sof/
 clone()
 {
-	# Check out Zephyr + SOF
-
 	type -p west || die "Install west and a west toolchain following https://docs.zephyrproject.org/latest/getting_started/index.html"
 	type -p git || die "Install git"
 
-	[ -e "$ZEPHYR_ROOT" ] && die "$ZEPHYR_ROOT already exists"
+	[ -e "$WEST_TOP" ] && die "$WEST_TOP already exists"
-	mkdir -p "$ZEPHYR_ROOT"
+	mkdir -p "$WEST_TOP"
-	cd "$ZEPHYR_ROOT"
+	git clone --depth=5 https://github.com/zephyrproject-rtos/zephyr \
-	west init
+	    "$WEST_TOP"/zephyr
-	west update
+	west init -l "${WEST_TOP}"/zephyr
-	cd modules/audio/sof
+	( cd "${WEST_TOP}"
-	git remote add sof https://github.com/thesofproject/sof.git
+	  mkdir -p modules/audio
-	git remote update sof
+	  ln -s ../../.. modules/audio/sof
-	git checkout sof/main
+	  # Do NOT "west update sof"!!
-	git clone --recurse-submodules https://github.com/thesofproject/rimage.git
+	  west update zephyr hal_xtensa
-	cd -
+	)
 }
 
 build()
 {
-	[ -d "$ZEPHYR_ROOT" ] || die "$ZEPHYR_ROOT doesn't exists"
+	cd "$WEST_TOP"
-	cd "$ZEPHYR_ROOT"
 
 	# Build rimage
 	RIMAGE_DIR=build-rimage
@@ -107,6 +111,8 @@ build()
 
 main()
 {
+	local zeproj
+
 	# parse the args
 	while getopts "acj:k:p:" OPTION; do
 		case "$OPTION" in
@@ -114,12 +120,28 @@ main()
 			c) DO_CLONE=yes ;;
 			j) BUILD_JOBS="$OPTARG" ;;
 			k) RIMAGE_KEY="$OPTARG" ;;
-			p) ZEPHYR_ROOT="$OPTARG" ;;
+			p) zeproj="$OPTARG" ;;
 			*) print_usage; exit 1 ;;
 		esac
 	done
 	shift $((OPTIND-1))
 
+	if [ -n "$zeproj" ] && [ x"$DO_CLONE" = xyes ]; then
+	    die 'Cannot use -p with -c, -c supports %s only' "${WEST_TOP}"
+	fi
+
+	if [ -n "$zeproj" ]; then
+
+	    [ -d "$zeproj" ] ||
+		die "$zeproj is not a directory, try -c instead of -p?"
+
+	    ( cd "$zeproj"
+	      test "$(realpath "$(west topdir)")" = "$(/bin/pwd)"
+	    ) || die '%s is not a zephyrproject' "$WEST_TOP"
+
+	    WEST_TOP="$zeproj"
+	fi
+
 	# parse platform args
 	for arg in "$@"; do
 		platform=none
@@ -148,6 +170,17 @@ main()
 
 	if [ "x$DO_CLONE" == "xyes" ]; then
 		clone
+	else
+		# Link to ourselves if no sof module yet
+		test -e "${WEST_TOP}"/modules/audio/sof ||
+		    ln -s "$SOF_TOP" "${WEST_TOP}"/modules/audio/sof
+
+		# Support for submodules in west is too recent, cannot
+		# rely on it
+		test -d "${WEST_TOP}"/modules/audio/sof/rimage/CMakeLists.txt || (
+		    cd "${WEST_TOP}"/modules/audio/sof
+		    git submodule update --init --recursive
+		)
 	fi
 
 	build