ci: disable ppc64 cross build for now

It's broken, see #839

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

.github/workflows/ci.yml

@@ -129,7 +129,7 @@ jobs:
         target:
           - i686-unknown-linux-gnu
           - powerpc-unknown-linux-gnu
-          - powerpc64-unknown-linux-gnu
+#          - powerpc64-unknown-linux-gnu
           - mips-unknown-linux-gnu
           - arm-linux-androideabi