gitlab-ci: enable assertions on fedora34-ninja jobs

We should have at least one CI job in merge request pipelines that
builds CMake with assertions enabled.  We avoid using the `Debug`
configuration in order to keep CI artifacts small, so instead use
the `Release` configuration without `-DNDEBUG`.

.gitlab/ci/configure_fedora34_ninja.cmake

@@ -1,6 +1,10 @@
 set(CMake_TEST_ISPC "ON" CACHE STRING "")
 set(CMake_TEST_GUI "ON" CACHE BOOL "")
 
+# "Release" flags without "-DNDEBUG" so we get assertions.
+set(CMAKE_C_FLAGS_RELEASE "-O3" CACHE STRING "")
+set(CMAKE_CXX_FLAGS_RELEASE "-O3" CACHE STRING "")
+
 # Cover compilation with C++11 only and not higher standards.
 set(CMAKE_CXX_STANDARD "11" CACHE STRING "")
 

.gitlab/os-linux.yml

@@ -131,6 +131,7 @@
 
     variables:
         CMAKE_CONFIGURATION: fedora34_ninja
+        CMAKE_CI_BUILD_TYPE: Release
         CTEST_NO_WARNINGS_ALLOWED: 1
 
 .fedora34_ninja_multi: