ci(cpp): pre-install cpr in CI workflow and finalize build validation

Author: bhardwajparth51

.github/workflows/sdk-build-validation.yml

@@ -169,6 +169,9 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y build-essential cmake libcurl4-openssl-dev nlohmann-json3-dev libgtest-dev
+          git clone --depth 1 --branch 1.10.5 https://github.com/libcpr/cpr.git /tmp/cpr
+          cmake -S /tmp/cpr -B /tmp/cpr/build -DCPR_BUILD_TESTS=OFF -DCPR_USE_SYSTEM_CURL=ON -DCMAKE_INSTALL_PREFIX=/usr/local
+          sudo cmake --build /tmp/cpr/build --target install -j$(nproc)
 
       - name: Build SDK
         working-directory: examples/${{ matrix.sdk }}