Quote the whole value:
cmake -DCMAKE_INSTALL_PREFIX=/g/g92/bhowmik1/installTF/ROSS \
-DCMAKE_C_FLAGS='-O3 -gcc-name=/path/bin/gcc' \
-DCMAKE_C_COMPILER=mpicc -DARCH=x86_64 -DROSS_BUILD_MODELS=ON ..
Quote the whole value:
cmake -DCMAKE_INSTALL_PREFIX=/g/g92/bhowmik1/installTF/ROSS \
-DCMAKE_C_FLAGS='-O3 -gcc-name=/path/bin/gcc' \
-DCMAKE_C_COMPILER=mpicc -DARCH=x86_64 -DROSS_BUILD_MODELS=ON ..