Use default-features=false on libz-sys to allow for zlib-ng

libz-sys enables the stock-zlib feature by default, which forces using
stock zlib and prevents using zlib-ng in compat mode. Disable
default-features, to allow the user of grpcio to determine what zlib
implementation to use.

Signed-off-by: Josh Triplett <[email protected]>

Author: joshtriplett

grpc-sys/Cargo.toml

@@ -50,7 +50,7 @@ exclude = [
 [dependencies]
 libc = "0.2"
 openssl-sys = { version = "0.9", optional = true, features = ["vendored"] }
-libz-sys = { version = "1.0.25", features = ["static"] }
+libz-sys = { version = "1.1.3", default-features = false, features = ["libc", "static"] }
 
 [features]
 default = ["use-bindgen"]