scripts/serve-docs.sh: ask bazel for the genfiles path 

...instead of assuming bazel-genfiles in `pwd`. In this
way, the script will also work with --symlink-prefix=/
set in the rc file.

--
Change-Id: I848a2e9791b4b8a8c1d6d0cea1f10117717935bd
Reviewed-on: https://cr.bazel.build/9118
PiperOrigin-RevId: 148894206
MOS_MIGRATED_REVID=148894206
diff --git a/scripts/serve-docs.sh b/scripts/serve-docs.sh
index 0ab17dc..4360653 100755
--- a/scripts/serve-docs.sh
+++ b/scripts/serve-docs.sh
@@ -47,7 +47,7 @@
 function build_and_serve {
   bazel build //site:jekyll-tree.tar
   rm -rf $WORKING_DIR/*
-  tar -xf bazel-genfiles/site/jekyll-tree.tar -C $WORKING_DIR
+  tar -xf "$(bazel info bazel-genfiles)/site/jekyll-tree.tar" -C $WORKING_DIR
 
   pkill -9 jekyll || true