Add standard cmake debug flags

tested, the cmake config shows this

-- Build Type: Debug (flags = '-g -O0')
-- Compiler Flags: -g -O0 -D__ROOFIT_NOBANNER -std=c++17 -Wno-implicit-fallthrough -Wno-noexcept-type -pipe  -Wshadow -Wall -W -Woverloaded-virtual -fsigned-char -pthread

root.spec

@@ -42,6 +42,8 @@ cmake ../%{n}-%{realversion} \
   -G Ninja \
   -DCMAKE_BUILD_TYPE=Debug \
   -DLLVM_BUILD_TYPE=Release \
+  -DCMAKE_C_FLAGS_DEBUG="-g -O0" \
+  -DCMAKE_CXX_FLAGS_DEBUG="-g -O0" \
   -DCMAKE_INSTALL_PREFIX="%{i}" \
   -DCMAKE_C_COMPILER=gcc \
   -DCMAKE_CXX_COMPILER=g++ \