Auto merge of #51757 - nielx:fix/haiku-fixes, r=nagisa

Haiku: several smaller fixes to build and run rust on Haiku

This PR combines three small patches that help Rust build and run on the Haiku platform. These patches do not intend to impact other platforms.

src/bootstrap/lib.rs

@@ -178,7 +178,7 @@
 #[cfg(windows)]
 mod job;
 
-#[cfg(unix)]
+#[cfg(all(unix, not(target_os = "haiku")))]
 mod job {
     use libc;
 
@@ -189,7 +189,7 @@ pub unsafe fn setup(build: &mut ::Build) {
     }
 }
 
-#[cfg(not(any(unix, windows)))]
+#[cfg(any(target_os = "haiku", not(any(unix, windows))))]
 mod job {
     pub unsafe fn setup(_build: &mut ::Build) {
     }

src/librustc_target/spec/x86_64_unknown_haiku.rs

@@ -16,6 +16,8 @@ pub fn target() -> TargetResult {
     base.max_atomic_width = Some(64);
     base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m64".to_string()]);
     base.stack_probes = true;
+    // This option is required to build executables on Haiku x86_64
+    base.position_independent_executables = true;
 
     Ok(Target {
         llvm_target: "x86_64-unknown-haiku".to_string(),

src/libstd/build.rs

@@ -121,7 +121,8 @@ fn build_libbacktrace(target: &str) -> Result<(), ()> {
     if !target.contains("apple-ios") &&
        !target.contains("solaris") &&
        !target.contains("redox") &&
-       !target.contains("android") {
+       !target.contains("android") &&
+       !target.contains("haiku") {
         build.define("HAVE_DL_ITERATE_PHDR", "1");
     }
     build.define("_GNU_SOURCE", "1");