build: remove zig wrapper and extra zig version file

These are obsolete. Please just use `anyzig`. You can get it at
https://github.com/marler8997/anyzig

build.zig.version

@@ -1 +0,0 @@
-0.15.1

zig

@@ -1,73 +0,0 @@
-#!/bin/bash
-set -e
-
-ARCH=$(uname -m)
-
-BASEDIR="$(cd "$(dirname "$0")" && pwd)"
-ZIGDIR=$BASEDIR/.cache/zig
-VERSION=$(<build.zig.version)
-
-OS=$(uname)
-
-if [ "$OS" == "Linux" ]; then
-    OS=linux
-elif [ "$OS" == "Darwin" ]; then
-    OS=macos
-elif [ "$OS" == "FreeBSD" ]; then
-    OS=freebsd
-    if [ "$ARCH" == "amd64" ]; then
-        ARCH=x86_64
-    fi
-fi
-
-if [ "$ARCH" == "arm64" ]; then
-    ARCH=aarch64
-fi
-
-ZIGVER="zig-$ARCH-$OS-$VERSION"
-ZIG=$ZIGDIR/$ZIGVER/zig
-
-if [ "$1" == "update" ]; then
-    curl -L --silent https://ziglang.org/download/index.json | jq -r '.master | .version' >build.zig.version
-    NEWVERSION=$(<build.zig.version)
-
-    if [ "$VERSION" != "$NEWVERSION" ]; then
-        echo "zig version updated from $VERSION to $NEWVERSION"
-        echo "rebuilding to update cdb..."
-        $0 cdb
-        exit 0
-    fi
-    echo "zig version $VERSION is up-to-date"
-    exit 0
-fi
-
-get_zig() {
-    (
-        mkdir -p "$ZIGDIR"
-        cd "$ZIGDIR"
-        TARBALL="https://ziglang.org/download/$VERSION/$ZIGVER.tar.xz"
-        if echo "$VERSION" | grep '\-dev\.' >&/dev/null; then
-            TARBALL="https://ziglang.org/builds/$ZIGVER.tar.xz"
-        fi
-        if [ ! -d "$ZIGVER" ]; then
-            curl "$TARBALL" | tar -xJ
-        fi
-    )
-}
-get_zig
-
-if [ "$1" == "cdb" ]; then
-    rm -rf .zig-cache
-    rm -rf .cache/cdb
-
-    $ZIG build
-
-    (
-        echo \[
-        cat .cache/cdb/*
-        echo {}\]
-    ) | perl -0777 -pe 's/,\n\{\}//igs' | jq . | grep -v 'no-default-config' >compile_commands.json
-    exit 0
-fi
-
-exec $ZIG "$@"