gbuild: disable -Werror for -Wdeprecated-declarations

Zillions of auto_ptr warnings in boost.

Change-Id: Ib9071c0241c2cb4c748f2634c1b39a2f8e889c20
Reviewed-on: https://gerrit.libreoffice.org/20737Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit ee26cbc5)

solenv/gbuild/platform/com_GCC_defs.mk

@@ -112,7 +112,7 @@ gb_CXXFLAGS_COMMON += -fstack-protector-strong
 gb_LinkTarget_LDFLAGS += -fstack-protector-strong
 endif
 
-gb_CFLAGS_WERROR := $(if $(ENABLE_WERROR),-Werror)
+gb_CFLAGS_WERROR := $(if $(ENABLE_WERROR),-Werror -Wno-error=deprecated-declarations)
 
 # This is the default in non-C++11 mode
 ifeq ($(COM_GCC_IS_CLANG),TRUE)