Add environment variable CG_RUN_IN_VM to run the test in a VM in the m68k CI

Author: antoyo

.github/workflows/m68k.yml

@@ -110,7 +110,7 @@ jobs:
 
         cd tests/hello-world
         CG_RUSTFLAGS="-Clinker=m68k-unknown-linux-gnu-gcc" ../../y.sh cargo build --target m68k-unknown-linux-gnu
-        CG_RUSTFLAGS="-Clinker=m68k-unknown-linux-gnu-gcc" ../../y.sh cargo run --target m68k-unknown-linux-gnu > hello_world_stdout
+        CG_RUN_IN_VM=1 CG_RUSTFLAGS="-Clinker=m68k-unknown-linux-gnu-gcc" ../../y.sh cargo run --target m68k-unknown-linux-gnu > hello_world_stdout
         test $(cat hello_world_stdout) == "Hello, world!" || exit 1
 
   # Summary job for the merge queue.

build_system/src/config.rs

@@ -378,6 +378,10 @@ impl ConfigInfo {
             self.run_in_vm = true;
         }
 
+        if std::env::var("CG_RUN_IN_VM").as_deref() == Ok("1") {
+            self.run_in_vm = true;
+        }
+
         let current_dir =
             std_env::current_dir().map_err(|error| format!("`current_dir` failed: {error:?}"))?;
         let channel = if self.channel == Channel::Release {