Add a hyperlight cfg for conditional compilation (#2)

* add a hyperlight cfg for conditional compilation

Signed-off-by: Jorge Prendes <jorge.prendes@gmail.com>

* test hyperlight cfg in guest example

Signed-off-by: Jorge Prendes <jorge.prendes@gmail.com>

---------

Signed-off-by: Jorge Prendes <jorge.prendes@gmail.com>

Author: jprendes

examples/guest/src/main.rs

@@ -3,6 +3,11 @@
 
 extern crate alloc;
 
+const _: () = {
+    #[cfg(not(hyperlight))]
+    compile_error!("This crate can only be compiled for hyperlight targets");
+};
+
 use alloc::format;
 use alloc::vec::Vec;
 

src/lib.rs

@@ -83,6 +83,8 @@ impl CargoCommandExt for std::process::Command {
     fn populate_from_args(&mut self, args: &Args) -> &mut Self {
         self.target(&args.target);
         self.sysroot(args.sysroot_dir());
+        self.append_rustflags("--cfg=hyperlight");
+        self.append_rustflags("--check-cfg=cfg(hyperlight)");
         self.entrypoint("entrypoint");
         if let Some(clang) = &args.clang {
             self.cc_env(&args.target, clang);

src/toolchain.rs

@@ -29,6 +29,8 @@ pub fn prepare(args: &Args) -> Result<()> {
         .arg("metadata")
         .manifest_path(&args.manifest_path)
         .arg("--format-version=1")
+        .append_rustflags("--cfg=hyperlight")
+        .append_rustflags("--check-cfg=cfg(hyperlight)")
         .checked_output()
         .context("Failed to get cargo metadata")?;