Auto merge of #31078 - nbaksalyar:illumos, r=alexcrichton

This pull request adds support for [Illumos](http://illumos.org/)-based operating systems: SmartOS, OpenIndiana, and others. For now it's x86-64 only, as I'm not sure if 32-bit installations are widespread. This PR is based on #28589 by @potatosalad, and also closes #21000, #25845, and #25846.

Required changes in libc are already merged: rust-lang/libc#138

Here's a snapshot required to build a stage0 compiler:
https://s3-eu-west-1.amazonaws.com/nbaksalyar/rustc-sunos-snapshot.tar.gz
It passes all checks from `make check`.

There are some changes I'm not quite sure about, e.g. macro usage in `src/libstd/num/f64.rs` and `DirEntry` structure in `src/libstd/sys/unix/fs.rs`, so any comments on how to rewrite it better would be greatly appreciated.

Also, LLVM configure script might need to be patched to build it successfully, or a pre-built libLLVM should be used. Some details can be found here: https://llvm.org/bugs/show_bug.cgi?id=25409

Thanks!

r? @brson

Author: bors

flock.rs

@@ -111,6 +111,25 @@ mod imp {
         pub const F_SETLKW: libc::c_int = 9;
     }
 
+    #[cfg(target_os = "solaris")]
+    mod os {
+        use libc;
+
+        pub struct flock {
+            pub l_type: libc::c_short,
+            pub l_whence: libc::c_short,
+            pub l_start: libc::off_t,
+            pub l_len: libc::off_t,
+            pub l_sysid: libc::c_int,
+            pub l_pid: libc::pid_t,
+        }
+
+        pub const F_WRLCK: libc::c_short = 2;
+        pub const F_UNLCK: libc::c_short = 3;
+        pub const F_SETLK: libc::c_int = 6;
+        pub const F_SETLKW: libc::c_int = 7;
+    }
+
     pub struct Lock {
         fd: libc::c_int,
     }