ci: Enable assertions in CMake build jobs on macOS

We did this previously on Linux and Windows:

* commit 45feab3c00 (gitlab-ci: enable assertions on fedora34-ninja jobs,
                     2022-01-31, v3.23.0-rc1~37^2)
* commit bec34592a6 (ci: Enable assertions in CMake build job on Windows,
                     2024-12-19)

The macOS build jobs were already building the `Release` configuration
by default.  Make it explicit to be sure we use these flags.

.gitlab/ci/configure_macos_arm64_ninja.cmake

@@ -11,5 +11,9 @@ set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STR
 set(CMake_TEST_TLS_VERSION "1.2" CACHE STRING "")
 set(CMake_TEST_TLS_VERSION_URL_BAD "https://badtls-v1-1.kitware.com:8011" CACHE STRING "")
 
+# "Release" flags without "-DNDEBUG" so we get assertions.
+set(CMAKE_C_FLAGS_RELEASE "-O3" CACHE STRING "")
+set(CMAKE_CXX_FLAGS_RELEASE "-O3" CACHE STRING "")
+
 include("${CMAKE_CURRENT_LIST_DIR}/configure_macos_common.cmake")
 include("${CMAKE_CURRENT_LIST_DIR}/configure_common.cmake")

.gitlab/ci/configure_macos_x86_64_ninja.cmake

@@ -14,5 +14,9 @@ set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STR
 set(CMake_TEST_TLS_VERSION "1.2" CACHE STRING "")
 set(CMake_TEST_TLS_VERSION_URL_BAD "https://badtls-v1-1.kitware.com:8011" CACHE STRING "")
 
+# "Release" flags without "-DNDEBUG" so we get assertions.
+set(CMAKE_C_FLAGS_RELEASE "-O3" CACHE STRING "")
+set(CMAKE_CXX_FLAGS_RELEASE "-O3" CACHE STRING "")
+
 include("${CMAKE_CURRENT_LIST_DIR}/configure_macos_common.cmake")
 include("${CMAKE_CURRENT_LIST_DIR}/configure_common.cmake")

.gitlab/os-macos.yml

@@ -29,6 +29,7 @@
 
     variables:
         CMAKE_CONFIGURATION: macos_x86_64_ninja
+        CMAKE_CI_BUILD_TYPE: Release
         CTEST_NO_WARNINGS_ALLOWED: 1
 
 .macos_arm64_ninja:
@@ -36,6 +37,7 @@
 
     variables:
         CMAKE_CONFIGURATION: macos_arm64_ninja
+        CMAKE_CI_BUILD_TYPE: Release
         CTEST_NO_WARNINGS_ALLOWED: 1
 
 .macos_arm64_ninja_symlinked: