curl-sys: remove Haiku cross-compilation workaround (#496)

Previously, there were issues cross-compiling the curl library from
source on the Haiku platform. That meant that a workaround was added to
`build.rs` to always link to the shared library in that case. When
testing for the current build, this workaround is no longer necessary,
as cross-compiling the curl-sys crate works as expected.

This removes the workaround for this scenario, as it can now use the
standard behavior.

Author: nielx

curl-sys/build.rs

@@ -5,7 +5,6 @@ use std::process::Command;
 
 fn main() {
     println!("cargo:rerun-if-changed=curl");
-    let host = env::var("HOST").unwrap();
     let target = env::var("TARGET").unwrap();
     let windows = target.contains("windows");
 
@@ -20,13 +19,6 @@ fn main() {
         return println!("cargo:rustc-flags=-l curl");
     }
 
-    // When cross-compiling for Haiku, use the system's default supplied
-    // libcurl (it supports http2). This is in the case where rustc and
-    // cargo are built for Haiku, which is done from a Linux host.
-    if host != target && target.contains("haiku") {
-        return println!("cargo:rustc-flags=-l curl");
-    }
-
     // If the static-curl feature is disabled, probe for a system-wide libcurl.
     if !cfg!(feature = "static-curl") {
         // OSX ships libcurl by default, so we just use that version