Add workaround for cross-rs/cross#1345 (#380)

Cargo.toml

@@ -51,3 +51,14 @@ test-in-browser = []
 [package.metadata.docs.rs]
 features = ["std", "custom"]
 rustdoc-args = ["--cfg", "docsrs"]
+
+# workaround for https://github.com/cross-rs/cross/issues/1345
+[package.metadata.cross.target.x86_64-unknown-netbsd]
+pre-build = [
+    "mkdir -p /tmp/netbsd",
+    "curl https://cdn.netbsd.org/pub/NetBSD/NetBSD-9.2/amd64/binary/sets/base.tar.xz -O",
+    "tar -C /tmp/netbsd -xJf base.tar.xz",
+    "cp /tmp/netbsd/usr/lib/libexecinfo.so /usr/local/x86_64-unknown-netbsd/lib",
+    "rm base.tar.xz",
+    "rm -rf /tmp/netbsd",
+]