ci: Fix Check ports syscfg update workflow

Changes the way 'cd' command is used, so it takes into account that each step is run in a separate shell instance.

.github/workflows/ports_syscfg_check.yml

@@ -52,21 +52,21 @@ jobs:
  newt upgrade --shallow=1
  rm -rf repos/apache-mynewt-nimble
  git clone .. repos/apache-mynewt-nimble
- cd ..
  - name: Build ports tests targets
  shell: bash
  run: |
  cd build
  ./repos/apache-mynewt-nimble/porting/update_generated_files.sh
- cd repos/apache-mynewt-nimble
  - name: Check ports syscfg (debug)
  shell: bash
  if: runner.debug == '1'
  run: |
+ cd build/repos/apache-mynewt-nimble
  git diff
  - name: Check ports syscfg
  shell: bash
  run: |
+ cd build/repos/apache-mynewt-nimble
  git diff --quiet || (\
  echo -e "\033[0;31mChanges in system configration files detected.";
  echo -e "\033[0;31mRun ./repos/apache-mynewt-nimble/porting/update_generated_files.sh" \