Write sha256 checksums for binaries

Author: Lee Miller

.buildbot/appimage/build.sh

@@ -45,4 +45,5 @@ set_sourceline
 ./${BUILDER} --recipe ${RECIPE}
 
 mkdir -p ../out
+sha256sum PyBitmessage*.AppImage > ../out/SHA256SUMS
 cp PyBitmessage*.AppImage ../out

.buildbot/winebuild/build.sh

@@ -3,4 +3,6 @@
 xvfb-run -a buildscripts/winbuild.sh || exit 1
 
 mkdir -p ../out
-mv packages/pyinstaller/dist/*.exe ../out
+mv packages/pyinstaller/dist/Bitmessage*.exe ../out
+cd ../out
+sha256sum Bitmessage*.exe > SHA256SUMS