chore(scripts): print wasm test filter path to stdout

The output of this script was pretty minimal because the filter build
path does not need to be known to run the test suite. This additional
output is helpful for local development, as users will now see a message
printed to stdout that looks something like this:

> Success! Test filters are now available at:
>
> /home/michaelm/git/kong/kong/spec/fixtures/proxy_wasm_filters/build
>
> For local development, set KONG_WASM_FILTERS_PATH accordingly:
>
> export KONG_WASM_FILTERS_PATH="/home/michaelm/git/kong/kong/spec/fixtures/proxy_wasm_filters/build"
>
> If testing with docker, make sure to mount the full (non-symlink) path
> inside your container:
>
> docker run \
>   -e KONG_WASM_FILTERS_PATH=/filters \
>   -v "$(realpath "/home/michaelm/git/kong/kong/spec/fixtures/proxy_wasm_filters/build"):/filters" \
>   ...

scripts/build-wasm-test-filters.sh

@@ -20,7 +20,7 @@
 set -euo pipefail
 
 readonly BUILD_TARGET=wasm32-wasi
-readonly FIXTURE_PATH=spec/fixtures/proxy_wasm_filters
+readonly FIXTURE_PATH=${PWD}/spec/fixtures/proxy_wasm_filters
 
 readonly INSTALL_ROOT=${PWD}/bazel-bin/build/kong-dev
 readonly TARGET_DIR=${INSTALL_ROOT}/wasm-cargo-target
@@ -111,10 +111,28 @@ main() {
         exit 1
     }
 
+    readonly symlink="$FIXTURE_PATH/build"
+
     # symlink the target to a standard location used in spec/kong_tests.conf
     ln -sfv \
         "$KONG_TEST_WASM_FILTERS_PATH" \
-        "$FIXTURE_PATH/build"
+        "$symlink"
+
+    echo "Success! Test filters are now available at:"
+    echo
+    echo "$symlink"
+    echo
+    echo "For local development, set KONG_WASM_FILTERS_PATH accordingly:"
+    echo
+    echo "export KONG_WASM_FILTERS_PATH=\"$symlink\""
+    echo
+    echo "If testing with docker, make sure to mount the full (non-symlink) path"
+    echo "inside your container:"
+    echo
+    echo "docker run \\"
+    echo "  -e KONG_WASM_FILTERS_PATH=/filters \\"
+    echo "  -v \"\$(realpath \"$symlink\"):/filters\" \\"
+    echo "  ..."
 }
 
 main