Do not use wildcard for missing toolchain dir

.gitlab-ci.yml

@@ -34,7 +34,7 @@ img:
         cargo install cargo-config xargo &&
         pushd bootloader-efi &&
         rustup update &&
-        mkdir -p "$HOME/.rustup/toolchains/nightly-*-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin" &&
         rustup component add rust-src &&
+        mkdir -p "$HOME/.rustup/toolchains/nightly-2017-11-29-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin" &&
         popd &&
         make ci-img IMG_TAG=$CI_COMMIT_REF_NAME