rust: make build.rs generic over various ./rust/projects

Guess the name of the subdir from the manifest directory, instead of
hard-coding it. In the following commits, other crates can then link to
this file, instead of maintaining their own copy.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Link: https://lore.kernel.org/r/20250827104147.717203-5-marcandre.lureau@redhat.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/rust/qemu-api/build.rs b/rust/qemu-api/build.rs
index 29d0945625..5654d1d562 100644
--- a/rust/qemu-api/build.rs
+++ b/rust/qemu-api/build.rs
@@ -9,12 +9,14 @@ use std::os::windows::fs::symlink_file;
 use std::{env, fs::remove_file, io::Result, path::Path};
 
 fn main() -> Result<()> {
+    let manifest_dir = env!("CARGO_MANIFEST_DIR");
     let file = if let Ok(root) = env::var("MESON_BUILD_ROOT") {
-        format!("{root}/rust/qemu-api/bindings.inc.rs")
+        let sub = get_rust_subdir(manifest_dir).unwrap();
+        format!("{root}/{sub}/bindings.inc.rs")
     } else {
         // Placing bindings.inc.rs in the source directory is supported
         // but not documented or encouraged.
-        format!("{}/src/bindings.inc.rs", env!("CARGO_MANIFEST_DIR"))
+        format!("{manifest_dir}/src/bindings.inc.rs")
     };
 
     let file = Path::new(&file);
@@ -41,3 +43,7 @@ fn main() -> Result<()> {
     println!("cargo:rerun-if-changed=build.rs");
     Ok(())
 }
+
+fn get_rust_subdir(path: &str) -> Option<&str> {
+    path.find("/rust").map(|index| &path[index + 1..])
+}