Add option to build toolchain tarball

Add TARBALL_RESULT option that will produce a tarball of the final
toolchain to make it easier to deploy the toolchain to other machines.

The implementation uses `find | sort` instead of `tar --sort` because
this was introduced in GNU Tar v1.28, which is not available in some LTS
Linux distributions. This is  a variation of the command recommended
here: https://wiki.debian.org/ReproducibleBuilds/FileOrderInTarballs

Closes #1262

Signed-off-by: Chris Packham <judge.packham@gmail.com>

config/global/paths.in

@@ -137,3 +137,31 @@ config STRIP_TARGET_TOOLCHAIN_EXECUTABLES
       An install-strip make target is provided that installs stripped
       executables, and may install libraries with unneeded or debugging
       sections stripped. 
+
+config TARBALL_RESULT
+    bool
+    depends on EXPERIMENTAL
+    prompt "Create binary toolchain tarball"
+    default n
+    help
+      Create tarball of the final binary toolchain.
+
+if TARBALL_RESULT
+
+config TARBALL_RESULT_DIR
+    string
+    depends on TARBALL_RESULT
+    prompt "Output directory"
+    default "${CT_TOP_DIR}"
+    help
+      Directory where tarball will be created.
+
+config TARBALL_RESULT_FILENAME
+    string
+    depends on TARBALL_RESULT
+    prompt "Output filename"
+    default "toolchain${CT_TOOLCHAIN_PKGVERSION:+-${CT_TOOLCHAIN_PKGVERSION}}-${CT_HOST:+HOST-${CT_HOST}-}${CT_TARGET}"
+    help
+      Filename for toolchain tarball, without extension.
+
+endif

scripts/build/internals.sh

@@ -31,6 +31,7 @@ do_finish() {
     local strip_args
     local gcc_version
     local exe_suffix
+    local tarball
 
     CT_DoStep INFO "Finalizing the toolchain's directory"
 
@@ -138,5 +139,19 @@ do_finish() {
         CT_InstallCopyingInformation
     fi
 
+    if [ "${CT_TARBALL_RESULT}" = y ]; then
+        tarball="${CT_TARBALL_RESULT_DIR}/${CT_TARBALL_RESULT_FILENAME}.tar.xz"
+        CT_DoLog EXTRA "Creating binary toolchain tarball: ${tarball}"
+        cp "${CT_TOP_DIR}/.config" "${CT_PREFIX_DIR}/${CT_TOOLCHAIN_PKGVERSION}.config"
+        (cd "${CT_PREFIX_DIR}" && \
+            find ./. -print0 | \
+                LC_ALL=C sort -z | \
+                tar --numeric-owner --owner=0 --group=0 \
+                    --transform "s,^\./\.,${CT_TARBALL_RESULT_FILENAME},S" \
+                    --no-recursion --null -T - -Jcf "${tarball}")
+        CT_DoLog EXTRA "Calculating binary toolchain checksum"
+        sha256sum "${tarball}" > "${tarball}.asc"
+    fi
+
     CT_EndStep
 }