fix installation of c toolchain

ci/install.sh

@@ -35,7 +35,7 @@ install_c_toolchain() {
             sudo apt-get install -y --no-install-recommends \
                  gcc-aarch64-linux-gnu libc6-dev-arm64-cross
             ;;
-        powerpc64-unknown-linux-gnu)
+        powerpc64le-unknown-linux-gnu)
             sudo apt-get install -y --no-install-recommends \
                  gcc-powerpc64le-linux-gnu libc6-dev-ppc64le-cross
             ;;