ci: update to sccache 0.2.15 on linux builds

The upstream release includes binaries for the architectures we need.
However, the binaries do not have execute permission in their tarballs,
so add it explicitly.

.gitlab/ci/sccache.sh

@@ -5,17 +5,16 @@ set -e
 readonly kernel="$(uname -s)-$(uname -m)"
 case $kernel in
     Linux-x86_64)
-        version="0.2.13"
+        version="v0.2.15"
         shatool="sha256sum"
-        sha256sum="28a5499e340865b08b632306b435913beb590fbd7b49a3f887a623b459fabdeb"
+        sha256sum="e5d03a9aa3b9fac7e490391bbe22d4f42c840d31ef9eaf127a03101930cbb7ca"
         platform="x86_64-unknown-linux-musl"
         ;;
     Linux-aarch64)
-        version="g6628e1f"
+        version="v0.2.15"
         shatool="sha256sum"
-        sha256sum="bb88adbb5a29c166ecaa78d0593493b609a7f84d91d1228502a908f319b513f0"
+        sha256sum="90d91d21a767e3f558196dbd52395f6475c08de5c4951a4c8049575fa6894489"
         platform="aarch64-unknown-linux-musl"
-        url="https://github.com/hwinit/sccache/releases/download/$version"
         ;;
     Darwin-x86_64)
         version="gfe63078"
@@ -49,3 +48,4 @@ curl -OL "$url/$tarball"
 $shatool --check sccache.sha256sum
 tar xf "$tarball"
 mv "$filename/sccache" .
+chmod +x sccache