Add a cross-compiling aarch64-apple-darwin CI builder

.github/workflows/ci.yml

@@ -89,6 +89,9 @@ jobs:
       - name: install sccache
         run: src/ci/scripts/install-sccache.sh
         if: success() && !env.SKIP_JOB
+      - name: select Xcode
+        run: src/ci/scripts/select-xcode.sh
+        if: success() && !env.SKIP_JOB
       - name: install clang
         run: src/ci/scripts/install-clang.sh
         if: success() && !env.SKIP_JOB
@@ -300,6 +303,18 @@ jobs:
               NO_LLVM_ASSERTIONS: 1
               NO_DEBUG_ASSERTIONS: 1
             os: macos-latest
+          - name: dist-aarch64-apple
+            env:
+              SCRIPT: "./x.py dist --stage 2"
+              RUST_CONFIGURE_ARGS: "--build=x86_64-apple-darwin --host=aarch64-apple-darwin --target=aarch64-apple-darwin --enable-sanitizers --enable-profiler --set rust.jemalloc --set llvm.ninja=false --tools=rls,clippy,rustfmt,analysis,src"
+              RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
+              SELECT_XCODE: /Applications/Xcode_12_beta.app
+              USE_XCODE_CLANG: 1
+              MACOSX_DEPLOYMENT_TARGET: 11.0
+              MACOSX_STD_DEPLOYMENT_TARGET: 11.0
+              NO_LLVM_ASSERTIONS: 1
+              NO_DEBUG_ASSERTIONS: 1
+            os: macos-latest
           - name: x86_64-msvc-1
             env:
               RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-msvc --enable-profiler"
@@ -437,6 +452,9 @@ jobs:
       - name: install sccache
         run: src/ci/scripts/install-sccache.sh
         if: success() && !env.SKIP_JOB
+      - name: select Xcode
+        run: src/ci/scripts/select-xcode.sh
+        if: success() && !env.SKIP_JOB
       - name: install clang
         run: src/ci/scripts/install-clang.sh
         if: success() && !env.SKIP_JOB
@@ -544,6 +562,9 @@ jobs:
       - name: install sccache
         run: src/ci/scripts/install-sccache.sh
         if: success() && !env.SKIP_JOB
+      - name: select Xcode
+        run: src/ci/scripts/select-xcode.sh
+        if: success() && !env.SKIP_JOB
       - name: install clang
         run: src/ci/scripts/install-clang.sh
         if: success() && !env.SKIP_JOB
@@ -648,6 +669,9 @@ jobs:
       - name: install sccache
         run: src/ci/scripts/install-sccache.sh
         if: success() && !env.SKIP_JOB
+      - name: select Xcode
+        run: src/ci/scripts/select-xcode.sh
+        if: success() && !env.SKIP_JOB
       - name: install clang
         run: src/ci/scripts/install-clang.sh
         if: success() && !env.SKIP_JOB

src/ci/github-actions/ci.yml

@@ -149,6 +149,10 @@ x--expand-yaml-anchors--remove:
         run: src/ci/scripts/install-sccache.sh
         <<: *step
 
+      - name: select Xcode
+        run: src/ci/scripts/select-xcode.sh
+        <<: *step
+
       - name: install clang
         run: src/ci/scripts/install-clang.sh
         <<: *step
@@ -457,6 +461,34 @@ jobs:
               NO_DEBUG_ASSERTIONS: 1
             <<: *job-macos-xl
 
+          # This target only needs to support 11.0 and up as nothing else supports the hardware
+          - name: dist-aarch64-apple
+            env:
+              SCRIPT: ./x.py dist --stage 2
+              RUST_CONFIGURE_ARGS: >-
+                --build=x86_64-apple-darwin
+                --host=aarch64-apple-darwin
+                --target=aarch64-apple-darwin
+                --enable-sanitizers
+                --enable-profiler
+                --set rust.jemalloc
+                --set llvm.ninja=false
+                --tools=rls,clippy,rustfmt,analysis,src
+              RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
+              SELECT_XCODE: /Applications/Xcode_12_beta.app
+              USE_XCODE_CLANG: 1
+              MACOSX_DEPLOYMENT_TARGET: 11.0
+              MACOSX_STD_DEPLOYMENT_TARGET: 11.0
+              NO_LLVM_ASSERTIONS: 1
+              NO_DEBUG_ASSERTIONS: 1
+              # TODO: Cargo is disabled until OpenSSL 1.1.1 can be
+              # compiled for aarch64-apple-darwin::
+              # https://github.com/openssl/openssl/pull/12369. Once
+              # fixed, remove `--tools`, add back
+              # `--enable-full-tools`, and enable this again
+              # DIST_REQUIRE_ALL_TOOLS: 1
+            <<: *job-macos-xl
+
           ######################
           #  Windows Builders  #
           ######################

src/ci/scripts/install-clang.sh

@@ -12,10 +12,18 @@ source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 LLVM_VERSION="10.0.0"
 
 if isMacOS; then
-    curl -f "${MIRRORS_BASE}/clang%2Bllvm-${LLVM_VERSION}-x86_64-apple-darwin.tar.xz" | tar xJf -
+    # If the job selects a specific Xcode version, use that instead of
+    # downloading our own version.
+    if [[ ${USE_XCODE_CLANG-0} -eq 1 ]]; then
+        bindir="$(xcode-select --print-path)/Toolchains/XcodeDefault.xctoolchain/usr/bin"
+    else
+        file="${MIRRORS_BASE}/clang%2Bllvm-${LLVM_VERSION}-x86_64-apple-darwin.tar.xz"
+        curl -f "${file}" | tar xJf -
+        bindir="$(pwd)/clang+llvm-${LLVM_VERSION}-x86_64-apple-darwin/bin"
+    fi
 
-    ciCommandSetEnv CC "$(pwd)/clang+llvm-${LLVM_VERSION}-x86_64-apple-darwin/bin/clang"
+    ciCommandSetEnv CC "${bindir}/clang"
-    ciCommandSetEnv CXX "$(pwd)/clang+llvm-${LLVM_VERSION}-x86_64-apple-darwin/bin/clang++"
+    ciCommandSetEnv CXX "${bindir}/clang++"
 
     # macOS 10.15 onwards doesn't have libraries in /usr/include anymore: those
     # are now located deep into the filesystem, under Xcode's own files. The

src/ci/scripts/select-xcode.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# This script selects the Xcode instance to use.
+
+set -euo pipefail
+IFS=$'\n\t'
+
+source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
+
+if isMacOS; then
+    if [[ -s "${SELECT_XCODE-}" ]]; then
+        sudo xcode-select -s "${SELECT_XCODE}"
+    fi
+fi