Add vendored cargo feature

Cargo.toml

@@ -35,6 +35,7 @@ bindgen = ["zstd-safe/bindgen"]
 debug = ["zstd-safe/debug"]
 legacy = ["zstd-safe/legacy"]
 pkg-config = ["zstd-safe/pkg-config"]
+vendored = ["zstd-safe/vendored"]
 wasm = []
 zstdmt = ["zstd-safe/zstdmt"]
 experimental = ["zstd-safe/experimental"]

zstd-safe/Cargo.toml

@@ -27,6 +27,7 @@ debug = ["zstd-sys/debug"]
 experimental = ["zstd-sys/experimental"]
 legacy = ["zstd-sys/legacy"]
 pkg-config = ["zstd-sys/pkg-config"]
+vendored = ["zstd-sys/vendored"]
 std = ["zstd-sys/std"] # Implements WriteBuf for std types like Cursor and Vec.
 zstdmt = ["zstd-sys/zstdmt"]
 thin = ["zstd-sys/thin"]

zstd-safe/zstd-sys/Cargo.toml

@@ -70,6 +70,7 @@ experimental = [] # Expose experimental ZSTD API
 legacy = [] # Enable legacy ZSTD support (for versions < zstd-0.8)
 non-cargo = [] # Silence cargo-specific build flags
 pkg-config = [] # Use pkg-config to build the zstd C library.
+vendored = [] # Always use vendored source code of zstd C library.
 std = [] # Deprecated: we never use types from std.
 zstdmt = [] # Enable multi-thread support (with pthread)
 thin = [] # Optimize binary by size

zstd-safe/zstd-sys/build.rs

@@ -257,7 +257,8 @@ fn main() {
     }
 
     // println!("cargo:rustc-link-lib=zstd");
-    let (defs, headerpaths) = if cfg!(feature = "pkg-config")
+    let (defs, headerpaths) = if (cfg!(feature = "pkg-config")
+        && !cfg!(feature = "vendored"))
         || env::var_os("ZSTD_SYS_USE_PKG_CONFIG").is_some()
     {
         pkg_config()