chore: gitignore makepkg build artifacts

Building packaging/PKGBUILD in place leaves scratch dirs (src/, pkg/,
peerspeak/ clone), the built *.pkg.tar.* and makepkg *.log behind, and
also rewrites pkgver in PKGBUILD. Ignore the scratch outputs so an
in-tree `makepkg` no longer pollutes git status. (Cleanest is still to
build from a copy outside the repo.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1 +1,8 @@
 /target
+
+# makepkg build artifacts (when building packaging/PKGBUILD in place)
+/packaging/src/
+/packaging/pkg/
+/packaging/peerspeak/
+/packaging/*.pkg.tar.*
+/packaging/*.log