Set XBUILD_SYSROOT_PATH when building bootloader (#41)

Author: phil-opp

src/builder.rs

@@ -222,7 +222,7 @@ impl Builder {
             cmd.arg("--release");
             cmd.env("KERNEL", kernel_bin_path);
             cmd.env_remove("RUSTFLAGS");
-            cmd.env("SYSROOT_DIR", target_dir.join("sysroot")); // for cargo-xbuild
+            cmd.env("XBUILD_SYSROOT_PATH", target_dir.join("bootloader-sysroot")); // for cargo-xbuild
             cmd
         };