add C++ source and compile job

Author: yaito3014

.github/workflows/test.yml

@@ -9,7 +9,16 @@ on:
       - main
 
 jobs:
+  compile:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: g++ -Wall -Wextra -o test source.cpp
+      - run: ./test
+
   test:
+    needs:
+      - compile
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

source.cpp

@@ -0,0 +1,6 @@
+#include <iostream>
+
+int main() {
+  int unused_variable = 42;
+  std::cout << "Hello, World!" << std::endl;
+}