create-spdx: default share_src for shared sources

if a source is using work-shared but isn't a kernel,
like for instance llvm-source from meta-clang, share_src was
previously undefined leading to a crash of the python code.
Default to WORKDIR and just override it in case the source being
a kernel recipe.
Additionally changes the variable names in the following, as
they imply that it's only about the kernel, which is not the case
in every case

(From OE-Core rev: 34fa68a0b07328c4ed4eef81f8cde80137a91f18)

(From OE-Core rev: 30cdb7fbec8e9cf5c5a25e28a1102fa562a7f6c2)

Signed-off-by: Konrad Weihmann <kweihmann@witekio.com>
On-behalf-of: Avnet Embedded <AvnetEmbedded@avnet.eu>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/create-spdx.bbclass

@@ -795,6 +795,7 @@ def spdx_get_src(d):
             bb.build.exec_func('do_unpack', d)
         # Copy source of kernel to spdx_workdir
         if is_work_shared_spdx(d):
+            share_src = d.getVar('WORKDIR')
             d.setVar('WORKDIR', spdx_workdir)
             d.setVar('STAGING_DIR_NATIVE', spdx_sysroot_native)
             src_dir = spdx_workdir + "/" + d.getVar('PN')+ "-" + d.getVar('PV') + "-" + d.getVar('PR')
@@ -802,8 +803,8 @@ def spdx_get_src(d):
             if bb.data.inherits_class('kernel',d):
                 share_src = d.getVar('STAGING_KERNEL_DIR')
             cmd_copy_share = "cp -rf " + share_src + "/* " + src_dir + "/"
-            cmd_copy_kernel_result = os.popen(cmd_copy_share).read()
-            bb.note("cmd_copy_kernel_result = " + cmd_copy_kernel_result)
+            cmd_copy_shared_res = os.popen(cmd_copy_share).read()
+            bb.note("cmd_copy_shared_result = " + cmd_copy_shared_res)
 
             git_path = src_dir + "/.git"
             if os.path.exists(git_path):