archiver.bbclass: adapt do_unpack_and_patch to RSS

do_unpack_and_patch was not correctly run until recently
("archiver.bbclass: various fixes for original+diff mode") but
with the fix applied, the errors we get indicate the function
is not adapted to work with recipe specific sysroots.

do_unpack_and_patch sets WORKDIR to ARCHIVER_WORKDIR which
affects all path settings relative to WORKDIR, inluding the paths
to recipes' sysroots. IOW, when do_unpack and do_patch are run, they
cannot find the necessary native tools and files located in the
sysroot (e.g., quiltrc) because the paths point to ARCHIVER_WORKDIR.

Adapt do_unpack_and_patch to RSS by restoring the original
STAGING_DIR_NATIVE after WORKDIR is changed to ARCHIVER_WORKDIR.

(From OE-Core rev: db7d2cc5a4df3c2077ba874c7ae395c73fd9ed13)

(From OE-Core rev: 7c0e3c5fa39e7ed3eedee8bac206476f70d1f422)

(From OE-Core rev: adb5234ac9c96f29336397552176ab5086772069)

Signed-off-by: Mikko Ylinen <mikko.ylinen@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/archiver.bbclass

@@ -315,12 +315,15 @@ python do_unpack_and_patch() {
         return
     ar_outdir = d.getVar('ARCHIVER_OUTDIR')
     ar_workdir = d.getVar('ARCHIVER_WORKDIR')
+    ar_sysroot_native = d.getVar('STAGING_DIR_NATIVE')
     pn = d.getVar('PN')
 
     # The kernel class functions require it to be on work-shared, so we dont change WORKDIR
     if not (bb.data.inherits_class('kernel-yocto', d) or pn.startswith('gcc-source')):
         # Change the WORKDIR to make do_unpack do_patch run in another dir.
         d.setVar('WORKDIR', ar_workdir)
+        # Restore the original path to recipe's native sysroot (it's relative to WORKDIR).
+        d.setVar('STAGING_DIR_NATIVE', ar_sysroot_native)
 
         # The changed 'WORKDIR' also caused 'B' changed, create dir 'B' for the
         # possibly requiring of the following tasks (such as some recipes's