image.py: write bitbake variables to .env file

Write set of bitbake variables used by wic into
build/tmp/sysroots/<machine>/imagedata/<image>.env

List of variables is defined in WICVARS variable in
meta/classes/image_types.bbclass.

This is needed for wic to be able to get bitbake variables without
running 'bitbake -e'.

(From OE-Core rev: 861ce6c5d4836df1a783be3b01d2de56117c9863)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/image_types.bbclass

@@ -248,3 +248,7 @@ IMAGE_EXTENSION_live = "hddimg iso"
 # The IMAGE_TYPES_MASKED variable will be used to mask out from the IMAGE_FSTYPES,
 # images that will not be built at do_rootfs time: vmdk, vdi, qcow2, hddimg, iso, etc.
 IMAGE_TYPES_MASKED ?= ""
+
+# The WICVARS variable is used to define list of bitbake variables used in wic code
+# variables from this list is written to <image>.env file
+WICVARS ?= "BBLAYERS DEPLOY_DIR_IMAGE HDDDIR IMAGE_BASENAME IMAGE_BOOT_FILES IMAGE_LINK_NAME IMAGE_ROOTFS INITRAMFS_FSTYPES INITRD ISODIR MACHINE_ARCH ROOTFS_SIZE STAGING_DATADIR STAGING_DIR_NATIVE STAGING_LIBDIR TARGET_SYS"

meta/lib/oe/image.py

@@ -326,6 +326,22 @@ class Image(ImageDepGraph):
 
         return image_cmd_groups
 
+    def _write_env(self):
+        """
+        Write environment variables used by wic
+        to tmp/sysroots/<machine>/imgdata/<image>.env
+        """
+        stdir = self.d.getVar('STAGING_DIR_TARGET', True)
+        outdir = os.path.join(stdir, 'imgdata')
+        if not os.path.exists(outdir):
+            os.makedirs(outdir)
+        basename = self.d.getVar('IMAGE_BASENAME', True)
+        with open(os.path.join(outdir, basename) + '.env', 'w') as envf:
+            for var in self.d.getVar('WICVARS', True).split():
+                value = self.d.getVar(var, True)
+                if value:
+                    envf.write('%s="%s"\n' % (var, value.strip()))
+
     def create(self):
         bb.note("###### Generate images #######")
         pre_process_cmds = self.d.getVar("IMAGE_PREPROCESS_COMMAND", True)
@@ -337,6 +353,8 @@ class Image(ImageDepGraph):
 
         image_cmd_groups = self._get_imagecmds()
 
+        self._write_env()
+
         for image_cmds in image_cmd_groups:
             # create the images in parallel
             nproc = multiprocessing.cpu_count()