C++: add deptrace pr-checks

tests/cpp-autobuild/src/build.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+errno || true  # just a command to check its autoinstallation by deptrace
+
+gcc -o main main.c

tests/cpp-autobuild/src/main.c

@@ -0,0 +1,8 @@
+#include "stdio.h"
+
+int main(int argc, char **argv) {
+    if (1) {
+        printf("Hello, World!\n");
+    }
+}
+