add link_cplusplus to fix exif link error

Cargo.lock

@@ -807,6 +807,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "link-cplusplus"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8cae2cd7ba2f3f63938b9c724475dfb7b9861b545a90324476324ed21dbc8c8"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "log"
 version = "0.4.14"
@@ -1074,6 +1083,7 @@ dependencies = [
  "int-enum",
  "json",
  "lazy_static",
+ "link-cplusplus",
  "regex",
  "reqwest",
  "spin_on",

Cargo.toml

@@ -29,7 +29,10 @@ cmake = "0.1"
 bindgen = "0.59"
 
 [features]
-exif = ["c_fixed_string", "int-enum", "utf16string"]
+exif = ["c_fixed_string", "link-cplusplus", "int-enum", "utf16string"]
 
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3.9", features = ["winnls", "stringapiset"] }
+
+[target.'cfg(target_env = "gnu")'.dependencies]
+link-cplusplus = { version = "1.0", features = ["libstdc++"], optional = true }

src/main.rs

@@ -8,6 +8,8 @@ extern crate json;
 extern crate int_enum;
 #[macro_use]
 extern crate lazy_static;
+#[cfg(all(feature = "link-cplusplus", target_env = "gnu"))]
+extern crate link_cplusplus;
 extern crate tokio;
 extern crate regex;
 extern crate reqwest;