adopt to new RPM 4.14 behavior for returning proper exit status

Since RPM 4.14, it started to return exit status of last executed
statement which on rawhide returns false so right condition doesn't
run.

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

rust-packaging.spec

@@ -55,7 +55,7 @@ lang=C.UTF-8
 lang=en_US.UTF-8
 %endif
 %endif
-[ -n "$lang" ] && sed -r -i -e "s|(%\{_bindir\}/cargo-inspector)|env LANG=$lang \1|" data/cargo.attr data/macros.cargo
+[ -z "$lang" ] || sed -r -i -e "s|(%\{_bindir\}/cargo-inspector)|env LANG=$lang \1|" data/cargo.attr data/macros.cargo
 
 %build
 %py3_build