ci: generalize ninja download script to support non-upstream builds

.gitlab/ci/ninja.sh

@@ -3,33 +3,32 @@
 set -e
 
 readonly version="1.10.2"
+baseurl="https://github.com/ninja-build/ninja/releases/download/v$version"
 
-case "$( uname -s )" in
-    Linux)
+case "$(uname -s)-$(uname -m)" in
+    Linux-x86_64)
         shatool="sha256sum"
         sha256sum="763464859c7ef2ea3a0a10f4df40d2025d3bb9438fcb1228404640410c0ec22d"
-        platform="linux"
+        filename="ninja-linux"
         ;;
-    Darwin)
+    Darwin-*)
         shatool="shasum -a 256"
         sha256sum="6fa359f491fac7e5185273c6421a000eea6a2f0febf0ac03ac900bd4d80ed2a5"
-        platform="mac"
+        filename="ninja-mac"
         ;;
     *)
-        echo "Unrecognized platform $( uname -s )"
+        echo "Unrecognized platform $(uname -s)-$(uname -m)"
         exit 1
         ;;
 esac
 readonly shatool
 readonly sha256sum
-readonly platform
 
-readonly filename="ninja-$platform"
 readonly tarball="$filename.zip"
 
 cd .gitlab
 
 echo "$sha256sum  $tarball" > ninja.sha256sum
-curl -OL "https://github.com/ninja-build/ninja/releases/download/v$version/$tarball"
+curl -OL "$baseurl/$tarball"
 $shatool --check ninja.sha256sum
 ./cmake/bin/cmake -E tar xf "$tarball"