ci: fix cross target

Author: Itsusinn

.cross/Dockerfile

@@ -3,16 +3,13 @@ ARG DEBIAN_FRONTEND=noninteractive
 
 FROM $CROSS_BASE_IMAGE
 
-ARG CROSS_BASE_IMAGE
-
 COPY .github/sccache.sh /
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends clang llvm && \
     rm -rf /var/lib/apt/lists/* && \
-    target="${CROSS_BASE_IMAGE##*/}" && \
     chmod +x /sccache.sh && \
-    /sccache.sh "${target%%:*}"
+    /sccache.sh "x86_64-unknown-linux-musl"
 
 ENV CC=clang \
     CXX=clang++ \