Adapt to new rustc-cdylib-link-arg parameter

After rust-lang/rust/pull/36574 has been merged the latest Rust
version 1.49 breaks the linking of dynamic libs in MacOS. These
changes ensure that the extra link args are applied only at the
dynamic lib generation linking step.

Author: lrascao

ct/rebar3_cargo_SUITE_data/test_nif_app/Cargo.lock

@@ -5,7 +5,7 @@ authors = ["Daniel Goertzen <[email protected]>"]
 
 [lib]
 name = "nifsys"
-crate-type = ["dylib"]
+crate-type = ["cdylib"]
 
 [dependencies]
 rustler = "0.21.1"

ct/rebar3_cargo_SUITE_data/test_nif_app/rust_src/nifsys/Cargo.toml

@@ -0,0 +1,11 @@
+use std::env;
+
+fn main() {
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
+
+    if target_os == "macos" {
+        println!("cargo:rustc-cdylib-link-arg=-flat_namespace");
+        println!("cargo:rustc-cdylib-link-arg=-undefined");
+        println!("cargo:rustc-cdylib-link-arg=suppress");
+    }
+}

ct/rebar3_cargo_SUITE_data/test_nif_app/rust_src/nifsys/build.rs

@@ -1,4 +1,8 @@
-{deps, [cargo]}.
+{deps, [
+    {cargo,
+        {git, "https://github.com/lrascao/erlang-cargo.git",
+            {branch, "fix/rustflags_hack"}}}
+]}.
 
 {eunit_tests, [rebar3_cargo]}.
 

rebar.config

@@ -1,11 +1,12 @@
 {"1.2.0",
-[{<<"cargo">>,{pkg,<<"cargo">>,<<"0.1.2">>},0},
+[{<<"cargo">>,
+  {git,"https://github.com/lrascao/erlang-cargo.git",
+       {ref,"8561886f8e415afbcd9e14af1ee3ebc590f4558d"}},
+  0},
  {<<"jsx">>,{pkg,<<"jsx">>,<<"2.11.0">>},1}]}.
 [
 {pkg_hash,[
- {<<"cargo">>, <<"1245B5A21454EBEABACF403911D54A82A0D457A3F635511A03AD06845F5ABF95">>},
  {<<"jsx">>, <<"08154624050333919B4AC1B789667D5F4DB166DC50E190C4D778D1587F102EE0">>}]},
 {pkg_hash_ext,[
- {<<"cargo">>, <<"EB614BA74F9F5B61643E5CC607BBF7DDC8420D368661E31C04E0DB7AD47E21B3">>},
  {<<"jsx">>, <<"EED26A0D04D217F9EECEFFFB89714452556CF90EB38F290A27A4D45B9988F8C0">>}]}
 ].