Fix C builds (#8795)

Missing stdbool.h for 'bool' in features .h, at least one user is arduinoWebSockets
Adds minimal headers sanity-check script to verify that C builds work as expected

Also noticed and removed default argument from crc32() in internal .h that may be used in .c
(not sure how extern C & default worked simultaniously, but at least in our .cpp Gcc somehow figured out it is a no overload solution)

.github/workflows/build-ide.yml

@@ -11,6 +11,22 @@ permissions:
 jobs:
 
   # Examples are built in parallel to avoid CI total job time limitation
+  sanity-check:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        shell: bash
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: false
+    - uses: actions/cache@v3
+      with:
+        path: ./tools/dist
+        key: ${{ runner.os }}-${{ hashFiles('package/package_esp8266com_index.template.json', 'tests/common.sh', 'tests/build.sh') }}
+    - name: Toolchain sanity checks
+      run: |
+        bash ./tests/sanity_check.sh
 
   build-linux:
     name: Linux - LwIP ${{ matrix.lwip }} (${{ matrix.chunk }})