Revert "[vm, gen_snapshot] Add app-aot-macho-dylib option for AOT snapshots."

This reverts commit 38ef28a058.

Reason for revert: Breaks build on debug mode 32-bit arches,
                   release mode simarm_x64

Issue: https://github.com/dart-lang/sdk/issues/60307
Original change's description:
> [vm, gen_snapshot] Add app-aot-macho-dylib option for AOT snapshots.
>
> This is the initial framework for creating snapshots as Mach-O dynamic
> libraries. Note that this framework is not 100% feature complete
> compared to generating Mach-O snapshots via assembly. In particular,
> the directly-compiled Mach-O dylib does not yet contain compact
> unwinding information.
>
> Other changes:
>
> * Adds UuidCommand to the native_stack_traces package's Mach-O reader,
>   which now appropriately returns the UUID as the build ID for Mach-O
>   shared objects.
>
> * Adds Utils::Basename(path) for portably retrieving the basename
>   from a path. (Returns nullptr for all arguments where it is not
>   currently implemented on Fuchsia or Windows.)
>
> * Adjusts vm/timeline.h to avoid pulling in <mach_o/loader.h> on MacOS,
>   as that interferes with uses of the namespaced Mach-O definitions
>   in platform/mach_o.h.
>
> * Only attempt to dlopen() a snapshot if ELF is the native format
>   for the host platform or the snapshot is not an ELF shared object.
>   If dlopen() is used, report the error message if it fails rather
>   than attempting to manually load the snapshot as an ELF shared object.
>
> * Fix the magic number stored in DylibAppSnapshot for loaded non-ELF
>   dynamic libraries.
>
> * Remove the detection of reverse-endian Mach-O magic numbers in
>   DartUtils::SniffForMagicNumber(), since all our Mach-O related code
>   assumes host-endian Mach-O files and so there's no point other than
>   to give a slightly better error message when failing.
>
> TEST=vm/dart/exported_symbols_test
>      vm/dart/unobfuscated_static_symbols_test
>      vm/dart/use_dwarf_stack_traces_flag_test
>      vm/cc/CanDetectMachOFiles
>
> Issue: https://github.com/dart-lang/sdk/issues/60307
> Change-Id: Idf5b49d6c6d035ab033509613212b95520d65965
> Cq-Include-Trybots: luci.dart.try:vm-aot-linux-debug-x64-try,vm-mac-release-arm64-try,vm-aot-mac-release-arm64-try,vm-aot-mac-release-x64-try,vm-aot-dwarf-linux-product-x64-try,vm-linux-debug-x64-try,vm-mac-debug-arm64-try,vm-fuchsia-release-x64-try,vm-fuchsia-release-arm64-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/415020
> Reviewed-by: Slava Egorov <vegorov@google.com>
> Commit-Queue: Tess Strickland <sstrickl@google.com>

Issue: https://github.com/dart-lang/sdk/issues/60307
Cq-Include-Trybots: luci.dart.try:vm-aot-linux-debug-x64-try,vm-mac-release-arm64-try,vm-aot-mac-release-arm64-try,vm-aot-mac-release-x64-try,vm-aot-dwarf-linux-product-x64-try,vm-linux-debug-x64-try,vm-mac-debug-arm64-try,vm-fuchsia-release-x64-try,vm-fuchsia-release-arm64-try
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: Iff2ab4c84a513a184784129f456bd357ae8e3a67
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/431220
Commit-Queue: Slava Egorov <vegorov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Tess Strickland <sstrickl@google.com>

runtime/vm/timeline.cc

@@ -16,10 +16,6 @@
 #include <tuple>
 #include <utility>
 
-#if defined(DART_HOST_OS_MACOS)
-#include <os/signpost.h>
-#endif
-
 #include "platform/atomic.h"
 #include "platform/hashmap.h"
 #include "vm/isolate.h"