Fix broken esp32-build workflow

Fixes the failing `Build ESP32 tests using idf.py with memory checks` step by exporting the rebar3
install directory to PATH.

Signed-off-by: Winford <winford@object.stream>

Author: UncleGrumpy

.github/workflows/esp32-build.yaml

@@ -135,6 +135,7 @@ jobs:
       working-directory: ./src/platforms/esp32/test/
       run: |
         set -e
+        export PATH=${PATH}:${HOME}/.cache/rebar3/bin
         cp sdkconfig.defaults sdkconfig.defaults.backup
         echo "CONFIG_COMPILER_STACK_CHECK_MODE_ALL=y" >> sdkconfig.defaults
         echo "CONFIG_COMPILER_STACK_CHECK=y" >> sdkconfig.defaults