Check the USE_SYSTEM_LIBNITROKEY environment variable

This patch introduces the USE_SYSTEM_LIBNITROKEY environment variable.
If it is set when compiling, the nitrokey-sys crate will not try to
build libnitrokey from source but instead uses the system libnitrokey
version.

1 files changed, 5 insertions, 0 deletions

diff --git a/build.rs b/build.rs
index af64a69..defce72 100644
--- a/build.rs
+++ b/build.rs
@@ -54,6 +54,11 @@ fn prepare_version_source(
 }
 
 fn main() {
+    if env::var("USE_SYSTEM_LIBNITROKEY").is_ok() {
+        println!("cargo:rustc-link-lib=nitrokey");
+        return;
+    }
+
     let out_dir = env::var("OUT_DIR").expect("Environment variable OUT_DIR is not set");
     let out_path = path::PathBuf::from(out_dir);