re-download Earthly on failure to execute (#1108)

Author: kevinAlbs

.evergreen/earthly.sh

@@ -32,6 +32,11 @@ if [[ "$OS_NAME" == "macos" ]]; then
 fi
 exe_path="$cache_dir/$exe_filename"
 
+if test -f "$exe_path" && ! "$exe_path" --version; then
+    echo "Failed to execute Earthly executable, removing and re-downloading"
+    rm "$exe_path"
+fi
+
 # Download if it isn't already present
 if ! test -f "$exe_path"; then
     echo "Downloading $exe_filename $EARTHLY_VERSION"