Override existing asar symlink in postinstall (#3369)

This ensures the link is correct. Should fix #3355.

ci/build/npm-postinstall.sh

@@ -56,18 +56,21 @@ main() {
   fi
 }
 
+# This is a copy of symlink_asar in ../lib.sh. Look there for details.
+symlink_asar() {
+  rm -f node_modules.asar
+  if [ "${WINDIR-}" ]; then
+    mklink /J node_modules.asar node_modules
+  else
+    ln -s node_modules node_modules.asar
+  fi
+}
+
 vscode_yarn() {
   cd lib/vscode
   yarn --production --frozen-lockfile
 
-  # This is a copy of symlink_asar in ../lib.sh. Look there for details.
-  if [ ! -e node_modules.asar ]; then
-    if [ "${WINDIR-}" ]; then
-      mklink /J node_modules.asar node_modules
-    else
-      ln -s node_modules node_modules.asar
-    fi
-  fi
+  symlink_asar
 
   cd extensions
   yarn --production --frozen-lockfile