Add an environment variable to keep the temp dir

README.md

@@ -49,6 +49,7 @@ panic_immediate_abort = false
 In addition to the above configuration keys, `cargo-xbuild` can be also configured through the following environment variables:
 
 - The `XBUILD_SYSROOT_PATH` variable can be used to specify where `cargo-xbuild` should place the generated sysroot. This variables takes precendence over the `package.metadata.cargo-xbuild.sysroot_path` configuration key.
+- When the `XBUILD_KEEP_TEMP` variable is set, the temporary directory used for compiling the sysroot is not deleted. This is useful for debugging. For convenience, `cargo-xbuild` also prints the directory name when the environment variable is set.
 
 ## Dev channel
 

src/sysroot.rs

@@ -62,8 +62,16 @@ fn build_crate(
     dst: &Path,
     verbose: bool,
 ) -> Result<()> {
-    let td = TempDir::new("xargo").chain_err(|| "couldn't create a temporary directory")?;
-    let td = td.path();
+    let td = TempDir::new("cargo-xbuild").chain_err(|| "couldn't create a temporary directory")?;
+    let td_path;
+    let td = if env::var_os("XBUILD_KEEP_TEMP").is_some() {
+        td_path = td.into_path();
+        println!("XBUILD_KEEP_TEMP: files at {:?}", td_path);
+        &td_path
+    } else {
+        td.path()
+    };
+
     let target_dir = td.join("target");
 
     if let Some(profile) = ctoml.profile() {