[wpimath] Use jinja for codegen (#3574)

While not really needed for wpimath, it will make more complex codegen
in the future significantly easier.

.github/workflows/sanitizers.yml

@@ -16,7 +16,7 @@ jobs:
             flags: "-DCMAKE_BUILD_TYPE=Ubsan"
     name: "${{ matrix.name }}"
     runs-on: ubuntu-latest
-    container: wpilib/roborio-cross-ubuntu:2021-18.04
+    container: wpilib/roborio-cross-ubuntu:2021-20.04
     steps:
       - uses: actions/checkout@v2
       - name: Install Dependencies
@@ -27,6 +27,12 @@ jobs:
             --install /usr/bin/gcc gcc /usr/bin/gcc-11 11 \
             --slave /usr/bin/g++ g++ /usr/bin/g++-11
           sudo update-alternatives --set gcc /usr/bin/gcc-11
+      - name: Set up Python 3.8
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+      - name: Install jinja
+        run: python -m pip install jinja2
       - name: configure
         run: mkdir build && cd build && cmake ${{ matrix.flags }} ..
       - name: build