Philippe 27/06/2019: use Fortran compiler instead of C one for libs4py linking

This allows successful compilation with (at least) ifort and gfortran

(cherry picked from commit 88a74de992b4d828b98a6e1906dcd61e2863f2f3)

src/Makefile

@@ -407,7 +407,7 @@ $(OBJDIR_MASTER)/spll_lockoff.o $(OBJDIR_MASTER)/spll_lockon.o $(OBJDIR_MASTER)/
 $(OBJDIR_MASTER)/fswap8buff.o $(OBJDIR_MASTER)/spll_remark2.o
 
 libs4py.so : progmaster
-	$(CC) -shared $(LDFLAGS) -o $(OBJDIR_MASTER)/$@ $(OBJ_S4PY) $(LIBS)
+	$(F90) -shared $(LDFLAGS) -o $(OBJDIR_MASTER)/$@ $(OBJ_S4PY) $(LIBS)
 endif
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