ci: Require macOS 11 for main precompiled binary

Xcode 27.0's libc++ no longer supports macOS 10.15 and below.

.gitlab/ci/configure_macos_package.cmake

@@ -1,5 +1,5 @@
 set(CPACK_SYSTEM_NAME "macos-universal" CACHE STRING "")
-set(CMAKE_OSX_DEPLOYMENT_TARGET "10.13" CACHE STRING "")
+set(CMAKE_OSX_DEPLOYMENT_TARGET "11" CACHE STRING "")
 set(CMake_GUI_OSX_DEPLOYMENT_TARGET "12" CACHE STRING "")
 set(CMAKE_C_STANDARD "11" CACHE STRING "")
 set(CMAKE_CXX_STANDARD "17" CACHE STRING "")

Help/release/dev/ci-xcode-27.rst

@@ -0,0 +1,6 @@
+ci-xcode-27
+-----------
+
+* The precompiled macOS binary provided on ``cmake.org`` now requires
+  macOS 11 or newer for command-line tools.  The :manual:`cmake-gui(1)`
+  application still requires macOS 12.