graphics/librsvg2-rust: fix build on powerpc64le and powerpc
- There are now two copies of cfg_expr used, both need to be patched.
- For some reason, when powerpc64le block in cfg_expr 0.9 was lower than it
is currently, the target failed to be identified as supported.
(cherry picked from commit 51cc50759b234fe474a8c64ca96633a2b9128e03)