[libc++] Remove unused macro in __config

[ldionne]

Summary

That macro was being defined but not used anywhere, so it must be
safe to remove it.

[jloser]

This is safe for libc++ use, so LGTM since CI is passing. As an aside, it looks like there are a few other spots in llvm that could benefit from the removal too:

git grep '__MAC_OS_X_VERSION_MIN_REQUIRED'
clang-tools-extra/clangd/unittests/JSONTransportTests.cpp:#if !(defined(_WIN32) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) &&          \
clang-tools-extra/clangd/unittests/JSONTransportTests.cpp:                          __MAC_OS_X_VERSION_MIN_REQUIRED < 101300))
llvm/lib/Support/LockFileManager.cpp:#if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)

[ldionne]

Remove uses of __MAC_OS_X_VERSION_MIN_REQUIRED in LLVM

[ldionne]

In D110289#3016525, @jloser wrote:

I think it's used in a few places from a quick git grep: [...]

__MAC_OS_X_VERSION_MIN_REQUIRED is defined by Apple's <Availability.h>. It is equivalent to __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__, which is set by the compiler. I suspect libc++ was defining it at some point for internal use (e.g. in the code I removed in https://reviews.llvm.org/rGebaf1d5e2b87), but now it's not needed anymore.

This is safe for libc++ use, so LGTM since CI is passing. As an aside, it looks like there are a few other spots in llvm that could benefit from the removal too:

git grep '__MAC_OS_X_VERSION_MIN_REQUIRED'
clang-tools-extra/clangd/unittests/JSONTransportTests.cpp:#if !(defined(_WIN32) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) &&          \
clang-tools-extra/clangd/unittests/JSONTransportTests.cpp:                          __MAC_OS_X_VERSION_MIN_REQUIRED < 101300))
llvm/lib/Support/LockFileManager.cpp:#if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)

Good point -- those could either have been using the value defined in <Availability.h> or unknowingly using the one set by libc++. I'll move those over to __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__, which is always defined by the compiler.

[ldionne]

Other CI failures appear unrelated to the change, so I'm shipping this.

clang-tools-extra/clangd/unittests/JSONTransportTests.cpp

 #include <cstdio>
 
 namespace clang {
 namespace clangd {
 namespace {
 
 // No fmemopen on windows or on versions of MacOS X earlier than 10.13, so we
 // can't easily run this test.
-#if !(defined(_WIN32) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) &&          \
-                          __MAC_OS_X_VERSION_MIN_REQUIRED < 101300))
+#if !(defined(_WIN32) || (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && \
+                          __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101300))
 
 // Fixture takes care of managing the input/output buffers for the transport.
 class JSONTransportTest : public ::testing::Test {
   std::string InBuf, OutBuf, MirrorBuf;
   llvm::raw_string_ostream Out, Mirror;
   std::unique_ptr<FILE, int (*)(FILE *)> In;
 
 protected:

libcxx/include/__config

 #elif defined(_LIBCPP_ABI_VCRUNTIME) && !defined(__cpp_aligned_new)
    // We're deferring to Microsoft's STL to provide aligned new et al. We don't
    // have it unless the language feature test macro is defined.
 #  define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
 #elif defined(__MVS__)
 #  define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
 #endif
 
-#if defined(__APPLE__)
-#  if !defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && \
-      defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
-#    define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
-#  endif
-#endif // defined(__APPLE__)
-
 #if defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION) || \
     (!defined(__cpp_aligned_new) || __cpp_aligned_new < 201606)
 #  define _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
 #endif
 
 #if defined(__APPLE__) || defined(__FreeBSD__)
 #define _LIBCPP_HAS_DEFAULTRUNELOCALE
 #endif

llvm/lib/Support/LockFileManager.cpp

 
 #ifdef _WIN32
 #include <windows.h>
 #endif
 #if LLVM_ON_UNIX
 #include <unistd.h>
 #endif
 
-#if defined(__APPLE__) && defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && (__MAC_OS_X_VERSION_MIN_REQUIRED > 1050)
+#if defined(__APPLE__) && defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ > 1050)
 #define USE_OSX_GETHOSTUUID 1
 #else
 #define USE_OSX_GETHOSTUUID 0
 #endif
 
 #if USE_OSX_GETHOSTUUID
 #include <uuid/uuid.h>
 #endif