build: Use gcc-9 and g++-9 on qemu workflow

Signed-off-by: Hiroshi Hatake <[email protected]>

.github/workflows/unit-tests.yaml

@@ -194,11 +194,11 @@ jobs:
             --volume "/etc/machine-id:/etc/machine-id"
           install: |
             apt-get update
-            apt-get install -y gcc-7 g++-7 libyaml-dev cmake flex bison libssl-dev #clang-6.0 libsystemd-dev
+            apt-get install -y gcc-9 g++-9 libyaml-dev cmake flex bison libssl-dev #clang-6.0 libsystemd-dev
             # ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer || true
 
-            update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 90
-            update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-7 90
+            update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 90
+            update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-9 90
             # update-alternatives --install /usr/bin/clang clang /usr/bin/clang-6.0 90
           run: |
             cd build