package/meson: import lzma only when needed

Fixes
http://autobuild.buildroot.net/results/49d/49d89e419edc34ec77129d748ac573f89dfddbae/
and many, many, many more.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
[Arnout: extend patch commit message]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/meson/0002-mdist.py-import-lzma-only-when-needed.patch

@@ -0,0 +1,50 @@
+From a3443360c8c0014638366d5bb2f5aa7683d5aec2 Mon Sep 17 00:00:00 2001
+From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+Date: Sat, 19 Oct 2019 09:52:06 +0200
+Subject: [PATCH] mdist.py: import lzma only when needed
+
+Importing lzma requires that python was built with lzma support. Buildroot
+builds its own version of python, without lzma support (i.e. without
+dependency on host-xz).
+
+lzma is anyway only needed to make the dist target, which we don't do in
+Buildroot. Therefore, in the Buildroot context, everything still works
+properly without lzma support.
+
+Moving the import down to the place where it is actually needed does not
+remove any functionality but fixes the problem for Buildroot.
+
+Source of patch:
+http://lists.busybox.net/pipermail/buildroot/2019-October/262990.html
+http://code.bulix.org/gdxcu4-914360
+
+Fixes https://github.com/mesonbuild/meson/issues/6012
+
+Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
+---
+ mesonbuild/mdist.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/mesonbuild/mdist.py b/mesonbuild/mdist.py
+index 7b753826..28e2fced 100644
+--- a/mesonbuild/mdist.py
++++ b/mesonbuild/mdist.py
+@@ -13,7 +13,6 @@
+ # limitations under the License.
+ 
+ 
+-import lzma
+ import gzip
+ import os
+ import sys
+@@ -133,6 +132,7 @@ def create_dist_hg(dist_name, archives, src_root, bld_root, dist_sub, dist_scrip
+     if dist_scripts:
+         mlog.warning('dist scripts are not supported in Mercurial projects')
+     if 'xztar' in archives:
++        import lzma
+         with lzma.open(xzname, 'wb') as xf, open(tarname, 'rb') as tf:
+             shutil.copyfileobj(tf, xf)
+         output_names.append(xzname)
+-- 
+2.20.1
+