remove upstream support for Zen hobby OS

The new plan to support hobby operating systems is #3784.

And what kind of name is "Zen" anyway? There's already a
[Zen programming language](http://zenlang.sourceforge.net/)
and that's just confusing.

lib/std/os.zig

@@ -31,7 +31,6 @@ pub const linux = @import("os/linux.zig");
 pub const uefi = @import("os/uefi.zig");
 pub const wasi = @import("os/wasi.zig");
 pub const windows = @import("os/windows.zig");
-pub const zen = @import("os/zen.zig");
 
 comptime {
     assert(@import("std") == std); // std lib tests require --override-lib-dir
@@ -45,7 +44,6 @@ test "" {
     _ = uefi;
     _ = wasi;
     _ = windows;
-    _ = zen;
 
     _ = @import("os/test.zig");
 }
@@ -59,7 +57,6 @@ pub const system = if (builtin.link_libc) std.c else switch (builtin.os) {
     .dragonfly => dragonfly,
     .wasi => wasi,
     .windows => windows,
-    .zen => zen,
     else => struct {},
 };
 

lib/std/target.zig

@@ -45,7 +45,6 @@ pub const Target = union(enum) {
         hurd,
         wasi,
         emscripten,
-        zen,
         uefi,
     };
 
@@ -432,7 +431,6 @@ pub const Target = union(enum) {
             .mesa3d,
             .contiki,
             .amdpal,
-            .zen,
             .hermit,
             => return .eabi,
             .openbsd,

src-self-hosted/c_int.zig

@@ -105,7 +105,6 @@ pub const CInt = struct {
             .macosx,
             .freebsd,
             .openbsd,
-            .zen,
             => switch (cint.id) {
                 .Short,
                 .UShort,

src-self-hosted/link.zig

@@ -304,13 +304,6 @@ fn constructLinkerArgsElf(ctx: *Context) !void {
     if (ctx.comp.target != Target.Native) {
         try ctx.args.append("--allow-shlib-undefined");
     }
-
-    if (ctx.comp.target.getOs() == .zen) {
-        try ctx.args.append("-e");
-        try ctx.args.append("_start");
-
-        try ctx.args.append("--image-base=0x10000000");
-    }
 }
 
 fn addPathJoin(ctx: *Context, dirname: []const u8, basename: []const u8) !void {

src/link.cpp

@@ -1831,12 +1831,6 @@ static void construct_linker_job_elf(LinkJob *lj) {
     if (!g->zig_target->is_native) {
         lj->args.append("--allow-shlib-undefined");
     }
-
-    if (g->zig_target->os == OsZen) {
-        lj->args.append("-e");
-        lj->args.append("_start");
-        lj->args.append("--image-base=0x10000000");
-    }
 }
 
 static void construct_linker_job_wasm(LinkJob *lj) {

src/target.cpp

@@ -179,7 +179,6 @@ static const Os os_list[] = {
     OsHurd,
     OsWASI,
     OsEmscripten,
-    OsZen,
     OsUefi,
 };
 
@@ -269,7 +268,6 @@ Os target_os_enum(size_t index) {
 ZigLLVM_OSType get_llvm_os_type(Os os_type) {
     switch (os_type) {
         case OsFreestanding:
-        case OsZen:
             return ZigLLVM_UnknownOS;
         case OsAnanas:
             return ZigLLVM_Ananas;
@@ -425,8 +423,6 @@ const char *target_os_name(Os os_type) {
     switch (os_type) {
         case OsFreestanding:
             return "freestanding";
-        case OsZen:
-            return "zen";
         case OsUefi:
             return "uefi";
         case OsAnanas:
@@ -1047,7 +1043,6 @@ uint32_t target_c_type_size_in_bits(const ZigTarget *target, CIntType id) {
             }
         case OsLinux:
         case OsMacOSX:
-        case OsZen:
         case OsFreeBSD:
         case OsNetBSD:
         case OsDragonFly:
@@ -1404,7 +1399,6 @@ const char *target_dynamic_linker(const ZigTarget *target) {
         case OsMesa3D:
         case OsContiki:
         case OsAMDPAL:
-        case OsZen:
         case OsHermitCore:
         case OsHurd:
         case OsWASI:
@@ -1655,7 +1649,6 @@ ZigLLVM_EnvironmentType target_default_abi(ZigLLVM_ArchType arch, Os os) {
         case OsMesa3D:
         case OsContiki:
         case OsAMDPAL:
-        case OsZen:
         case OsHermitCore:
             return ZigLLVM_EABI;
         case OsOpenBSD:

src/target.hpp

@@ -49,7 +49,6 @@ enum Os {
     OsHurd,
     OsWASI,
     OsEmscripten,
-    OsZen,
     OsUefi,
 };