libcxx: Update to Clang 20.

See:

* https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc/77319
* https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701

We're dropping support for C++03 for Zig due to the first change; it would be
insane to ship 1018 duplicate header files just for this outdated use case.

As a result of the second change, I had to bring in a subset of the headers from
llvm-libc since libc++ now depends on these. Hopefully we can continue to get
away with not copying the entirety of llvm-libc.

1 files changed, 1 insertions, 23 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index d7f3ee6dde..d5a21aef9c 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -5776,29 +5776,7 @@ pub fn addCCArgs(
                     comp.zig_lib_directory.path.?, "libcxxabi", "include",
                 }));
 
-                if (target.abi.isMusl()) {
-                    try argv.append("-D_LIBCPP_HAS_MUSL_LIBC");
-                }
-
-                try argv.append("-D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS");
-                try argv.append("-D_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS");
-                try argv.append("-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS");
-
-                if (!comp.config.any_non_single_threaded) {
-                    try argv.append("-D_LIBCPP_HAS_NO_THREADS");
-                }
-
-                // See the comment in libcxx.zig for more details about this.
-                try argv.append("-D_LIBCPP_PSTL_BACKEND_SERIAL");
-
-                try argv.append(try std.fmt.allocPrint(arena, "-D_LIBCPP_ABI_VERSION={d}", .{
-                    @intFromEnum(comp.libcxx_abi_version),
-                }));
-                try argv.append(try std.fmt.allocPrint(arena, "-D_LIBCPP_ABI_NAMESPACE=__{d}", .{
-                    @intFromEnum(comp.libcxx_abi_version),
-                }));
-
-                try argv.append(libcxx.hardeningModeFlag(mod.optimize_mode));
+                try libcxx.addCxxArgs(comp, arena, argv);
             }
 
             // According to Rich Felker libc headers are supposed to go before C language headers.