[libc++] Remove the ability to not install the support headers

Those are part of the library, and shipping them just adds a tiny bit of
size to the distribution. This was originally added in b422ecc to
make it possible to match the Makefile build, which doesn't exist anymore.

The upside is build system simplification.

Author: ldionne

libcxx/CMakeLists.txt

@@ -159,7 +159,6 @@ cmake_dependent_option(LIBCXX_INSTALL_STATIC_LIBRARY
 cmake_dependent_option(LIBCXX_INSTALL_SHARED_LIBRARY
   "Install the shared libc++ library." ON
   "LIBCXX_ENABLE_SHARED;LIBCXX_INSTALL_LIBRARY" OFF)
-option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
 cmake_dependent_option(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY
         "Install libc++experimental.a" ON
         "LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY;LIBCXX_INSTALL_LIBRARY" OFF)
@@ -390,11 +389,6 @@ if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY AND LIBCXX_ENABLE_ABI_LINKER_SC
         LIBCXX_ENABLE_ABI_LINKER_SCRIPT")
 endif()
 
-if (LIBCXX_HAS_MUSL_LIBC AND NOT LIBCXX_INSTALL_SUPPORT_HEADERS)
-  message(FATAL_ERROR "LIBCXX_INSTALL_SUPPORT_HEADERS can not be turned off"
-                      "when building for Musl with LIBCXX_HAS_MUSL_LIBC.")
-endif()
-
 if (LIBCXX_ABI_FORCE_ITANIUM AND LIBCXX_ABI_FORCE_MICROSOFT)
   message(FATAL_ERROR "Only one of LIBCXX_ABI_FORCE_ITANIUM and LIBCXX_ABI_FORCE_MICROSOFT can be specified.")
 endif ()

libcxx/include/CMakeLists.txt

@@ -2,8 +2,8 @@ set(files
   __bit_reference
   __bsd_locale_defaults.h
   __bsd_locale_fallbacks.h
-  __errc
   __debug
+  __errc
   __functional_03
   __functional_base
   __functional_base_03
@@ -144,6 +144,22 @@ set(files
   string.h
   string_view
   strstream
+  support/android/locale_bionic.h
+  support/fuchsia/xlocale.h
+  support/ibm/limits.h
+  support/ibm/locale_mgmt_aix.h
+  support/ibm/support.h
+  support/ibm/xlocale.h
+  support/musl/xlocale.h
+  support/newlib/xlocale.h
+  support/solaris/floatingpoint.h
+  support/solaris/wchar.h
+  support/solaris/xlocale.h
+  support/win32/limits_msvc_win32.h
+  support/win32/locale_win32.h
+  support/xlocale/__nop_locale_mgmt.h
+  support/xlocale/__posix_l_fallback.h
+  support/xlocale/__strtonum_fallback.h
   system_error
   tgmath.h
   thread
@@ -162,28 +178,6 @@ set(files
   wctype.h
   )
 
-if(LIBCXX_INSTALL_SUPPORT_HEADERS)
-  set(files
-    ${files}
-    support/android/locale_bionic.h
-    support/fuchsia/xlocale.h
-    support/ibm/limits.h
-    support/ibm/locale_mgmt_aix.h
-    support/ibm/support.h
-    support/ibm/xlocale.h
-    support/musl/xlocale.h
-    support/newlib/xlocale.h
-    support/solaris/floatingpoint.h
-    support/solaris/wchar.h
-    support/solaris/xlocale.h
-    support/win32/limits_msvc_win32.h
-    support/win32/locale_win32.h
-    support/xlocale/__nop_locale_mgmt.h
-    support/xlocale/__posix_l_fallback.h
-    support/xlocale/__strtonum_fallback.h
-    )
-endif()
-
 configure_file("__config_site.in"
                "${LIBCXX_BINARY_DIR}/__config_site"
                @ONLY)