fix: make shims cargo test --workspace compatible

Signed-off-by: Harald Hoyer <harald@profian.com>

crates/shim-kvm/build.rs

@@ -1,10 +1,15 @@
 // SPDX-License-Identifier: Apache-2.0
 
+use std::env::var;
+
 fn main() {
-    println!(
-        "cargo:rustc-link-arg-bin=enarx-shim-kvm=-T{}/layout.ld",
-        std::env::var("CARGO_MANIFEST_DIR").unwrap()
-    );
-    println!("cargo:rustc-link-arg-bin=enarx-shim-kvm=-Wl,--sort-section=alignment");
-    println!("cargo:rustc-link-arg-bin=enarx-shim-kvm=-nostartfiles");
+    let target_os = var("CARGO_CFG_TARGET_OS").expect("missing CARGO_CFG_TARGET_OS");
+    if target_os == "none" {
+        println!(
+            "cargo:rustc-link-arg-bin=enarx-shim-kvm=-T{}/layout.ld",
+            std::env::var("CARGO_MANIFEST_DIR").unwrap()
+        );
+        println!("cargo:rustc-link-arg-bin=enarx-shim-kvm=-Wl,--sort-section=alignment");
+        println!("cargo:rustc-link-arg-bin=enarx-shim-kvm=-nostartfiles");
+    }
 }

crates/shim-kvm/src/main.rs

@@ -7,7 +7,7 @@
 #![deny(clippy::all)]
 #![deny(missing_docs)]
 #![warn(rust_2018_idioms)]
-#![no_main]
+#![cfg_attr(target_os = "none", no_main)]
 #![feature(asm_const)]
 #![cfg_attr(coverage, feature(no_coverage))]
 
@@ -102,6 +102,7 @@ unsafe fn switch_shim_stack(ip: extern "sysv64" fn() -> !, sp: u64) -> ! {
 ///
 /// # Safety
 /// Do not call from Rust.
+#[cfg(target_os = "none")]
 #[cfg_attr(coverage, no_coverage)]
 unsafe extern "sysv64" fn _pre_main(c_bit_mask: u64) -> ! {
     C_BIT_MASK.store(c_bit_mask, Ordering::Relaxed);
@@ -115,7 +116,11 @@ unsafe extern "sysv64" fn _pre_main(c_bit_mask: u64) -> ! {
     switch_shim_stack(main, gdt::INITIAL_STACK.pointer.as_u64())
 }
 
+#[cfg(not(target_os = "none"))]
+pub fn main() {}
+
 /// The main function for the shim with stack setup
+#[cfg(target_os = "none")]
 #[cfg_attr(coverage, no_coverage)]
 extern "sysv64" fn main() -> ! {
     unsafe { gdt::init() };
@@ -194,6 +199,7 @@ macro_rules! correct_table_c_bit {
     };
 }
 
+#[cfg(target_os = "none")]
 // The initial function called at startup
 //
 // It sets up essential registers, page tables and jumps in shim virtual address space

crates/shim-sgx/build.rs

@@ -1,10 +1,16 @@
 // SPDX-License-Identifier: Apache-2.0
 
+use std::env::var;
+
 fn main() {
-    println!(
-        "cargo:rustc-link-arg-bin=enarx-shim-sgx=-T{}/layout.ld",
-        std::env::var("CARGO_MANIFEST_DIR").unwrap()
-    );
-    println!("cargo:rustc-link-arg-bin=enarx-shim-sgx=-Wl,--sort-section=alignment");
-    println!("cargo:rustc-link-arg-bin=enarx-shim-sgx=-nostartfiles");
+    let target_os = var("CARGO_CFG_TARGET_OS").expect("missing CARGO_CFG_TARGET_OS");
+
+    if target_os == "none" {
+        println!(
+            "cargo:rustc-link-arg-bin=enarx-shim-sgx=-T{}/layout.ld",
+            std::env::var("CARGO_MANIFEST_DIR").unwrap()
+        );
+        println!("cargo:rustc-link-arg-bin=enarx-shim-sgx=-Wl,--sort-section=alignment");
+        println!("cargo:rustc-link-arg-bin=enarx-shim-sgx=-nostartfiles");
+    }
 }

crates/shim-sgx/src/main.rs

@@ -10,7 +10,7 @@
 #![deny(clippy::all)]
 #![deny(missing_docs)]
 #![warn(rust_2018_idioms)]
-#![no_main]
+#![cfg_attr(target_os = "none", no_main)]
 
 #[allow(unused_extern_crates)]
 extern crate rcrt1;
@@ -193,6 +193,8 @@ extern "sysv64" {
     /// Do not call this function from Rust. It is the entry point for SGX.
     pub fn _start();
 }
+
+#[cfg(target_os = "none")]
 global_asm!(
         ".pushsection .text.startup,\"ax\",@progbits",
         ".global _start",
@@ -295,6 +297,10 @@ fn validate_block_ptr(ptr: *mut u8) -> &'static mut [usize; BLOCK_SIZE / size_of
     unsafe { &mut *(ptr as *mut [usize; BLOCK_SIZE / size_of::<usize>()]) }
 }
 
+#[cfg(not(target_os = "none"))]
+pub fn main() {}
+
+#[cfg(target_os = "none")]
 unsafe extern "C" fn main(
     block_ptr: *mut u8,
     ssas: &mut [StateSaveArea; NUM_SSA],