depends: use -Xclang -fno-cxx-modules in macOS cross build

Newer versions of the macOS SDK, have introduced code like:
```cpp
if defined(__has_feature) && __has_feature(modules)
define USE_CLANG_TYPES 1
else
define USE_CLANG_TYPES 0
endif

if USE_CLANG_TYPES
include <sys/_types/_ptrdiff_t.h>
include <sys/_types/_size_t.h>
include <sys/_types/_va_list.h>
include <sys/_types/_wchar_t.h>
endif
```

which is currently causing compile failures due to undeclared types,
which manifest when C++ modules are enabled. Note that the usage of
"modules" in LLVM is can be a bit ambiguous, see:
https://github.com/llvm/llvm-project/issues/55891.

For now, explcitly disable cxx modules using `-fno-cxx-modules`. This
resolves the include/compilation issues.

Related discussion:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116827
https://github.com/llvm/llvm-project/pull/150349
https://github.com/llvm/llvm-project/issues/57432

depends/hosts/darwin.mk

@@ -50,6 +50,12 @@ darwin_STRIP=$(shell $(SHELL) $(.SHELLFLAGS) "command -v llvm-strip")
 #
 #         Disable adhoc codesigning (for now) when using LLVM tooling, to avoid
 #         non-determinism issues with the Identifier field.
+#
+#     -Xclang -fno-cxx-modules
+#
+#         Disable C++ modules. We don't use these, and modules cause definition issues
+#         in the SDK, where __has_feature(modules) is used to define USE_CLANG_TYPES,
+#         which is in turn used as an include guard.
 
 darwin_CC=$(clang_prog) --target=$(host) \
               -isysroot$(OSX_SDK) -nostdlibinc \
@@ -61,7 +67,7 @@ darwin_CXX=$(clangxx_prog) --target=$(host) \
                -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
 darwin_CFLAGS=-mmacos-version-min=$(OSX_MIN_VERSION)
-darwin_CXXFLAGS=-mmacos-version-min=$(OSX_MIN_VERSION)
+darwin_CXXFLAGS=-mmacos-version-min=$(OSX_MIN_VERSION) -Xclang -fno-cxx-modules
 darwin_LDFLAGS=-Wl,-platform_version,macos,$(OSX_MIN_VERSION),$(OSX_SDK_VERSION)
 
 ifneq ($(build_os),darwin)