revert #170

This caused fairly widespread problems and it seems that the original
issue that led to this change (rust-lang/rust#69552)
should really be fixed by better defining the data exported from eg:
libz-sys rather than having downstream crates replicating the same logic
from inside that crate.

refs: #174
refs: #170
refs: #169
refs: rust-lang/rust#69552

libssh2-sys/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libssh2-sys"
-version = "0.2.16"
+version = "0.2.17"
 authors = ["Alex Crichton <[email protected]>", "Wez Furlong <[email protected]>"]
 links = "ssh2"
 build = "build.rs"

libssh2-sys/build.rs

@@ -124,10 +124,6 @@ fn main() {
     println!("cargo:rerun-if-env-changed=DEP_Z_INCLUDE");
     if let Some(path) = env::var_os("DEP_Z_INCLUDE") {
         cfg.include(path);
-    } else if let Ok(lib) = pkg_config::find_library("zlib") {
-        for path in &lib.include_paths {
-            cfg.include(path);
-        }
     }
 
     println!("cargo:rerun-if-env-changed=DEP_OPENSSL_INCLUDE");
@@ -139,10 +135,6 @@ fn main() {
                 }
             }
         }
-    } else if let Ok(lib) = pkg_config::find_library("openssl") {
-        for path in &lib.include_paths {
-            cfg.include(path);
-        }
     }
 
     let libssh2h = fs::read_to_string("libssh2/include/libssh2.h").unwrap();