ci: check if we got the proper paths

Author: crepererum

.github/actions/free-disk-space/free.sh

@@ -5,11 +5,6 @@ set -euo pipefail
 df -h
 
 to_delete=(
-  "/lib/firefox"
-  "/lib/google-cloud-sdk"
-  "/lib/jvm"
-  "/lib/llvm-16"
-  "/lib/llvm-17"
   "/opt/az"
   "/opt/google"
   "/opt/hostedtoolcache/CodeQL"
@@ -19,6 +14,11 @@ to_delete=(
   "/opt/hostedtoolcache/node"
   "/opt/microsoft"
   "/opt/pipx"
+  "/usr/lib/firefox"
+  "/usr/lib/google-cloud-sdk"
+  "/usr/lib/jvm"
+  "/usr/lib/llvm-16"
+  "/usr/lib/llvm-17"
   "/usr/local/.ghcup"
   "/usr/local/lib/android"
   "/usr/share/swift"
@@ -37,6 +37,12 @@ for d in "${to_delete[@]}"; do
     exit 1
   fi
 
+  r="$(realpath "$d")"
+  if [ "$d" != "$r" ]; then
+    echo "not a canonical path, use this instead: $r"
+    exit 1
+  fi
+
   sudo rm -rf "$d"
 done