Use single threads for testing

Author: Susurrus

Cross.toml

@@ -0,0 +1,2 @@
+[build.env]
+passthrough = ["RUST_TEST_THREADS"]

ci/script.sh

@@ -8,6 +8,9 @@ main() {
         export RUSTFLAGS=--cfg=travis
     fi
 
+    # Use only a single thread for testing as we get spurious failures otherwise
+    export RUST_TEST_THREADS=1
+
     # Build debug and release targets
     cross build --target $TARGET
     cross build --target $TARGET --release