ci: macos: take advantage of zig-bootstrap

ci/azure/macos_script

@@ -3,26 +3,23 @@
 set -x
 set -e
 
-brew install s3cmd gcc@10
+brew install s3cmd
 
 ZIGDIR="$(pwd)"
-LLVMVER="11.0.0"
 ARCH="x86_64"
-CACHE_BASENAME="llvm+clang+lld-$LLVMVER-$ARCH-macosx-gcc10-release"
+CACHE_BASENAME="zig+llvm+lld+clang-$ARCH-macos-gnu-0.6.0+0f4386875f"
 PREFIX="$HOME/$CACHE_BASENAME"
 JOBS="-j2"
 
-# I tried using the system default compiler (clang), but it couldn't statically link libc++.
-# So we use gcc-10 from homebrew.
-export CC=gcc-10
-export CXX=g++-10
-
 rm -rf $PREFIX
-
 cd $HOME
 wget -nv "https://ziglang.org/deps/$CACHE_BASENAME.tar.xz"
 tar xf "$CACHE_BASENAME.tar.xz"
 
+ZIG="$PREFIX/bin/zig"
+export CC="$ZIG cc"
+export CXX="$ZIG c++"
+
 cd $ZIGDIR
 
 # Make the `zig version` number consistent.
@@ -31,7 +28,18 @@ git config core.abbrev 9
 
 mkdir build
 cd build
-cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH=$PREFIX -DCMAKE_INSTALL_PREFIX=$(pwd)/release -DZIG_STATIC=ON -DZIG_TARGET_TRIPLE=x86_64-macos.10.15.7-gnu
+cmake .. \
+  -DCMAKE_INSTALL_PREFIX="$(pwd)/release" \
+  -DCMAKE_PREFIX_PATH="$PREFIX" \
+  -DCMAKE_CROSSCOMPILING=True \
+  -DCMAKE_SYSTEM_NAME="Darwin" \
+  -DCMAKE_AR="$PREFIX/bin/llvm-ar" \
+  -DCMAKE_RANLIB="$PREFIX/bin/llvm-ranlib" \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DZIG_TARGET_TRIPLE="$ARCH-macos.10.15.7-gnu" \
+  -DZIG_TARGET_MCPU="baseline" \
+  -DZIG_EXECUTABLE="$ZIG"
+
 make $JOBS install
 release/bin/zig build test