Fix Darwin builds for non-standard environments (e.g. Nix) (#941)

* Fix Darwin builds for non-standard environments (e.g. Nix) * Conditionally add _DARWIN_C_SOURCE define * Also for darwin OS --------- Co-authored-by: Justin Smith <justsmth@amazon.com> Co-authored-by: Justin W Smith <103147162+justsmth@users.noreply.github.com>

Author: martinjlowm

aws-lc-sys/builder/cc_builder.rs

@@ -222,6 +222,11 @@ impl CcBuilder {
  }
  }
 
+ if target_os() == "macos" || target_os() == "darwin" {
+ // Certain MacOS system headers are guarded by _POSIX_C_SOURCE and _DARWIN_C_SOURCE
+ build_options.push(BuildOption::define("_DARWIN_C_SOURCE", "1"));
+ }
+
  let opt_level = cargo_env("OPT_LEVEL");
  match opt_level.as_str() {
  "0" | "1" | "2" => {
@@ -403,6 +408,10 @@ impl CcBuilder {
  };
 
  je_builder.define("AWSLC", "1");
+ if target_os() == "macos" || target_os() == "darwin" {
+ // Certain MacOS system headers are guarded by _POSIX_C_SOURCE and _DARWIN_C_SOURCE
+ je_builder.define("_DARWIN_C_SOURCE", "1");
+ }
  je_builder.pic(true);
  if target_os() == "windows" && compiler.is_like_msvc() {
  je_builder.flag("/Od").flag("/W4").flag("/DYNAMICBASE");