ci: Fix building PWM example

Signed-off-by: Robert Winkler <rwinkler@antmicro.com>

.github/workflows/pipeline.yml

@@ -95,6 +95,7 @@ jobs:
           docker run --rm -i -v $(pwd):/wrk -w /wrk \
           gcr.io/hdl-containers/conda/f4pga/xc7/z010 \
           bash -le <<'EOF'
+            pip3 install -e .
             pip3 install -r requirements.impl.txt
             cd examples/pwm
             make zvb