Add workaround for linking against macOS SDK's relocatable dylibs

See rust-lang/cargo#5077 (comment)
and rust-lang/rust#127100

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/merge_requests/1538>

Author: amyspark

Cargo.lock

@@ -56,6 +56,12 @@ windows = { version = "0.58", features=["Win32_Graphics_Direct3D11",
 cocoa = "0.25"
 objc = "0.2.7"
 
+[target.'cfg(target_os = "macos")'.build-dependencies]
+system-deps = "7"
+
+[package.metadata.system-deps]
+"gstreamer-1.0" = "1.14"
+
 [build-dependencies]
 gl_generator = { version = "0.14", optional = true }
 

examples/Cargo.toml

@@ -19,4 +19,22 @@ fn generate_gl_bindings() {}
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     generate_gl_bindings();
+
+    // https://github.com/rust-lang/cargo/issues/5077#issuecomment-1284482987
+    #[cfg(all(not(docsrs), target_os = "macos"))]
+    match system_deps::Config::new().probe() {
+        Ok(deps) => {
+            let usr = std::path::Path::new("/usr/lib");
+            let usr_local = std::path::Path::new("/usr/local/lib");
+            for dep in deps.all_link_paths() {
+                if dep != &usr && dep != &usr_local {
+                    println!("cargo:rustc-link-arg=-Wl,-rpath,{:?}", dep.as_os_str());
+                }
+            }
+        }
+        Err(s) => {
+            println!("cargo:warning={s}");
+            std::process::exit(1);
+        }
+    }
 }

examples/build.rs

@@ -23,6 +23,12 @@ futures = "0.3"
 cocoa = "0.25"
 objc = "0.2.7"
 
+[target.'cfg(target_os = "macos")'.build-dependencies]
+system-deps = "7"
+
+[package.metadata.system-deps]
+"gstreamer-1.0" = "1.14"
+
 [[bin]]
 name = "basic-tutorial-13"
 required-features = ["termion"]

tutorials/Cargo.toml

@@ -0,0 +1,23 @@
+#[cfg(docsrs)]
+fn main() {} // prevent linking libraries to avoid documentation failure
+
+// https://github.com/rust-lang/cargo/issues/5077#issuecomment-1284482987
+#[cfg(not(docsrs))]
+fn main() {
+    #[cfg(target_os = "macos")]
+    match system_deps::Config::new().probe() {
+        Ok(deps) => {
+            let usr = std::path::Path::new("/usr/lib");
+            let usr_local = std::path::Path::new("/usr/local/lib");
+            for dep in deps.all_link_paths() {
+                if dep != &usr && dep != &usr_local {
+                    println!("cargo:rustc-link-arg=-Wl,-rpath,{:?}", dep.as_os_str());
+                }
+            }
+        }
+        Err(s) => {
+            println!("cargo:warning={s}");
+            std::process::exit(1);
+        }
+    }
+}