macOS package: fix compilation of x13as against gfortran 10

Add -std=legacy to FFLAGS.

Do the same for the Windows package, even though we don’t yet use version 10 of
gfortran (but that will of course happen at some point).

(manually cherry picked from commit 9b946ca0)

macOS/deps/Makefile

-# Copyright © 2019 Dynare Team
+# Copyright © 2019-2020 Dynare Team
 #
 # This file is part of Dynare.
 #
@@ -144,7 +144,7 @@ sources64/x13as-$(X13AS_VERSION): tarballs/x13assrc_V$(X13AS_VERSION).tar.gz
 
 lib64/x13as/x13as: sources64/x13as-$(X13AS_VERSION)
 	cd $< && sed -i '' 's/-static//g' makefile.gf
-	make -C $< -f makefile.gf FC=gfortran LINKER=ld FFLAGS="-O2" LDFLAGS="-macosx_version_min 10.14.0 -lSystem $(shell gfortran -print-file-name=libgfortran.a) $(shell gfortran -print-file-name=libquadmath.a) $(shell gfortran -print-libgcc-file-name) $(shell gfortran -print-file-name=libgcc_eh.a)" PROGRAM=x13as
+	make -C $< -f makefile.gf FC=gfortran LINKER=ld FFLAGS="-O2 -std=legacy" LDFLAGS="-macosx_version_min 10.14.0 -lSystem $(shell gfortran -print-file-name=libgfortran.a) $(shell gfortran -print-file-name=libquadmath.a) $(shell gfortran -print-libgcc-file-name) $(shell gfortran -print-file-name=libgcc_eh.a)" PROGRAM=x13as
 	strip $</x13as
 	mkdir -p $(dir $@)
 	cp $</x13as $@

windows/deps/Makefile

@@ -277,13 +277,13 @@ sources64/x13as-$(X13AS_VERSION): tarballs/x13assrc_V$(X13AS_VERSION).tar.gz
 	tar xf $< --directory $@
 
 lib32/x13as/x13as.exe: sources32/x13as-$(X13AS_VERSION)
-	make -C $< -f makefile.gf FC=i686-w64-mingw32-gfortran LINKER=i686-w64-mingw32-gfortran FFLAGS="-O2" PROGRAM=x13as.exe
+	make -C $< -f makefile.gf FC=i686-w64-mingw32-gfortran LINKER=i686-w64-mingw32-gfortran FFLAGS="-O2 -std=legacy" PROGRAM=x13as.exe
 	i686-w64-mingw32-strip $</x13as.exe
 	mkdir -p $(dir $@)
 	cp $</x13as.exe $@
 
 lib64/x13as/x13as.exe: sources64/x13as-$(X13AS_VERSION)
-	make -C $< -f makefile.gf FC=x86_64-w64-mingw32-gfortran LINKER=x86_64-w64-mingw32-gfortran FFLAGS="-O2" PROGRAM=x13as.exe
+	make -C $< -f makefile.gf FC=x86_64-w64-mingw32-gfortran LINKER=x86_64-w64-mingw32-gfortran FFLAGS="-O2 -std=legacy" PROGRAM=x13as.exe
 	x86_64-w64-mingw32-strip $</x13as.exe
 	mkdir -p $(dir $@)
 	cp $</x13as.exe $@