[GHA] Use -GNinja in nightly workflow

Workaround an upstream LLVM change which does not play well with the
default `-G"Unix Makefiles"` CMake generator by using `-GNinja` instead.

Author: kbenzie

.github/workflows/e2e_core.yml

@@ -115,6 +115,7 @@ jobs:
       run: >
         cmake
         -B build
+        -GNinja
         -DCMAKE_C_COMPILER=${{matrix.compiler.c}}
         -DCMAKE_CXX_COMPILER=${{matrix.compiler.cxx}}
         -DCMAKE_BUILD_TYPE=${{matrix.build_type}}