newlib: use RIOT dependency system for _GNU_SOURCE instead

Makefile.dep

@@ -8,6 +8,12 @@ OLD_USEPKG := $(sort $(USEPKG))
 # pull dependencies from drivers
 include $(RIOTBASE)/drivers/Makefile.dep
 
+ifneq (,$(filter cbor_ctime,$(USEMODULE)))
+  ifneq (,$(filter newlib,$(USEMODULE)))
+    USEMODULE += newlib_gnu_source
+  endif
+endif
+
 ifneq (,$(filter csma_sender,$(USEMODULE)))
   USEMODULE += random
   USEMODULE += xtimer
@@ -381,6 +387,10 @@ ifneq (,$(filter od,$(USEMODULE)))
   USEMODULE += fmt
 endif
 
+ifneq (,$(filter newlib_gnu_source,$(USEMODULE)))
+  USEMODULE += newlib
+endif
+
 ifneq (,$(filter newlib_nano,$(USEMODULE)))
   USEMODULE += newlib
 endif

makefiles/libc/newlib.mk

@@ -9,6 +9,10 @@ ifneq (,$(filter newlib_nano,$(USEMODULE)))
   endif
 endif
 
+ifneq (,$(filter newlib_gnu_source,$(USEMODULE)))
+  CFLAGS += -D_GNU_SOURCE=1
+endif
+
 ifeq (1,$(USE_NEWLIB_NANO))
   export LINKFLAGS += -specs=nano.specs
 endif

makefiles/pseudomodules.inc.mk

@@ -52,6 +52,7 @@ PSEUDOMODULES += netstats_l2
 PSEUDOMODULES += netstats_ipv6
 PSEUDOMODULES += netstats_rpl
 PSEUDOMODULES += newlib
+PSEUDOMODULES += newlib_gnu_source
 PSEUDOMODULES += newlib_nano
 PSEUDOMODULES += openthread
 PSEUDOMODULES += pktqueue