rust: remove libunwind

fixes: https://github.com/void-linux/void-packages/issues/3605

[ci skip]

srcpkgs/rust/patches/libunwind.patch

@@ -0,0 +1,75 @@
+we use libgcc_s for unwind, no need for libunwind.a
+https://github.com/void-linux/void-packages/issues/3605
+
+
+--- rustc-1.28.0-src/src/libunwind/build.rs.orig	2018-10-11 10:37:16.617653976 +0200
++++ rustc-1.28.0-src/src/libunwind/build.rs	2018-10-11 10:37:33.584492467 +0200
+@@ -15,9 +15,7 @@
+     let target = env::var("TARGET").expect("TARGET was not set");
+ 
+     if target.contains("linux") {
+-        if target.contains("musl") {
+-            // musl is handled in lib.rs
+-        } else if !target.contains("android") {
++        if !target.contains("android") {
+             println!("cargo:rustc-link-lib=gcc_s");
+         }
+     } else if target.contains("freebsd") {
+--- rustc-1.28.0-src/src/libunwind/lib.rs.orig	2018-10-11 10:37:51.012326568 +0200
++++ rustc-1.28.0-src/src/libunwind/lib.rs	2018-10-11 10:38:03.512207577 +0200
+@@ -33,8 +33,3 @@
+         pub use libunwind::*;
+     }
+ }
+-
+-#[cfg(target_env = "musl")]
+-#[link(name = "unwind", kind = "static", cfg(target_feature = "crt-static"))]
+-#[link(name = "gcc_s", cfg(not(target_feature = "crt-static")))]
+-extern {}
+
+--- rustc-1.28.0-src/src/bootstrap/sanity.rs.orig	2018-10-11 10:29:34.169735519 +0200
++++ rustc-1.28.0-src/src/bootstrap/sanity.rs	2018-10-11 10:30:02.467509880 +0200
+@@ -21,7 +21,7 @@
+ use std::collections::HashMap;
+ use std::env;
+ use std::ffi::{OsString, OsStr};
+-use std::fs::{self, File};
++use std::fs::File;
+ use std::io::Read;
+ use std::path::PathBuf;
+ use std::process::Command;
+@@ -186,34 +186,6 @@
+             }
+         }
+ 
+-        // Make sure musl-root is valid
+-        if target.contains("musl") {
+-            // If this is a native target (host is also musl) and no musl-root is given,
+-            // fall back to the system toolchain in /usr before giving up
+-            if build.musl_root(*target).is_none() && build.config.build == *target {
+-                let target = build.config.target_config.entry(target.clone())
+-                                 .or_insert(Default::default());
+-                target.musl_root = Some("/usr".into());
+-            }
+-            match build.musl_root(*target) {
+-                Some(root) => {
+-                    if fs::metadata(root.join("lib/libc.a")).is_err() {
+-                        panic!("couldn't find libc.a in musl dir: {}",
+-                               root.join("lib").display());
+-                    }
+-                    if fs::metadata(root.join("lib/libunwind.a")).is_err() {
+-                        panic!("couldn't find libunwind.a in musl dir: {}",
+-                               root.join("lib").display());
+-                    }
+-                }
+-                None => {
+-                    panic!("when targeting MUSL either the rust.musl-root \
+-                            option or the target.$TARGET.musl-root option must \
+-                            be specified in config.toml")
+-                }
+-            }
+-        }
+-
+         if target.contains("msvc") {
+             // There are three builds of cmake on windows: MSVC, MinGW, and
+             // Cygwin. The Cygwin build does not have generators for Visual

srcpkgs/rust/template

@@ -12,7 +12,7 @@ patch_args="-Np1"
 build_style=configure
 make_build_args="dist VERBOSE=1"
 hostmakedepends="cmake curl pkg-config python"
-makedepends="libffi-devel llvm ncurses-devel libxml2-devel libunwind-devel zlib-devel"
+makedepends="libffi-devel llvm ncurses-devel libxml2-devel zlib-devel"
 short_desc="Safe, concurrent, practical systems language"
 maintainer="Enno Boland <gottox@voidlinux.eu>"
 homepage="https://www.rust-lang.org/"
@@ -24,7 +24,7 @@ if [ "$CROSS_BUILD" ]; then
 	hostmakedepends+=" cargo llvm"
 
 	# These are required for building the buildhost's stage0/1
-	hostmakedepends+=" libffi-devel libxml2-devel libunwind-devel
+	hostmakedepends+=" libffi-devel libxml2-devel 
 		ncurses-devel zlib-devel"
 else
 	case "$XBPS_MACHINE" in