Update libc++ to 24c12bfb (5 Feb 2022).

Notable changes:
* make _LIBCPP_ABI_UNSTABLE set _LIBCPP_ABI_VERSION
* replace include utility with specific includes in __utility folder
* disallow ranges:begin for array of incomplete types
* move fpos to separate header
* delete optional usage of type builtins that were never implemented
* define ranges::views namespace in its own header
* remove base class of the vector

ref:1d141d911ba017f306cca431c3b56c25d495e54e

contrib/libs/cxxsupp/libcxx/import

@@ -1,6 +1,6 @@
 #!/bin/sh -e
 
-rev=eaadc451
+rev=24c12bfb
 output_dir="libcxx-r$rev"
 if [ -z $1 ] ; then
     git clone https://github.com/llvm/llvm-project.git --no-checkout "$output_dir/tmp"

contrib/libs/cxxsupp/libcxx/include/__algorithm/adjacent_find.h

@@ -15,7 +15,7 @@
 #include <__iterator/iterator_traits.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/all_of.h

@@ -13,7 +13,7 @@
 #include <__config>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/any_of.h

@@ -13,7 +13,7 @@
 #include <__config>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/binary_search.h

@@ -16,7 +16,7 @@
 #include <__iterator/iterator_traits.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/clamp.h

@@ -14,7 +14,7 @@
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/comp.h

@@ -12,7 +12,7 @@
 #include <__config>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/comp_ref_type.h

@@ -17,7 +17,7 @@
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/copy.h

@@ -16,7 +16,7 @@
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

contrib/libs/cxxsupp/libcxx/include/__algorithm/copy_backward.h

@@ -16,7 +16,7 @@
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
+#  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD