Hydro_RNSD passes CFLAGS to LD

[Roland Haas]

Hydro_RNSID passed CFLAGS to LD when linking its utilities:

HYDRO_RNS_LDFLAGS := $(HYDRO_RNS_CFLAGS) $(DEBUG_LD) $(LDFLAGS) $(EXTRAFLAGS) $(GENERAL_LIBRARIES

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this fails if LD is nvcc which will not accept a -std=gnu99 or -std=c99 option typically present in CFLAGS since it only accepts C++ language flavors.

This is similar to #2553 where Cactus pass CPPFLAGS and CXXFLAGS to LD