depends: add C_STANDARD and CXX_STANDARD

See bitcoin/bitcoin#22380. GNU flavor is used for the C standard as
OpenSSL have troubles building without it.

depends/Makefile

@@ -12,6 +12,9 @@ NO_WALLET ?=
 NO_UPNP ?=
 FALLBACK_DOWNLOAD_PATH ?= https://bitcoincore.org/depends-sources
 
+C_STANDARD ?= gnu11
+CXX_STANDARD ?= c++17
+
 BUILD = $(shell ./config.guess)
 HOST ?= $(BUILD)
 PATCHES_PATH = $(BASEDIR)/patches

depends/README.md

@@ -60,6 +60,8 @@ The following can be set when running make: make FOO=bar
     BASE_CACHE: built packages will be placed here
     SDK_PATH: Path where sdk's can be found (used by macOS)
     FALLBACK_DOWNLOAD_PATH: If a source file can't be fetched, try here before giving up
+    C_STANDARD: Set the C standard version used. Defaults to `c11`.
+    CXX_STANDARD: Set the C++ standard version used. Defaults to `c++17`.
     NO_QT: Don't download/build/cache qt and its dependencies
     NO_WALLET: Don't download/build/cache libs needed to enable the wallet
     NO_UPNP: Don't download/build/cache packages needed for enabling upnp

depends/hosts/darwin.mk

@@ -115,8 +115,8 @@ darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
                -Xclang -internal-externc-isystem$(clang_resource_dir)/include \
                -Xclang -internal-externc-isystem$(OSX_SDK)/usr/include
 
-darwin_CFLAGS=-pipe
-darwin_CXXFLAGS=$(darwin_CFLAGS)
+darwin_CFLAGS=-pipe -std=$(C_STANDARD)
+darwin_CXXFLAGS=-pipe -std=$(CXX_STANDARD)
 
 darwin_release_CFLAGS=-O2
 darwin_release_CXXFLAGS=$(darwin_release_CFLAGS)

depends/hosts/linux.mk

@@ -1,5 +1,5 @@
-linux_CFLAGS=-pipe
-linux_CXXFLAGS=$(linux_CFLAGS)
+linux_CFLAGS=-pipe -std=$(C_STANDARD)
+linux_CXXFLAGS=-pipe -std=$(CXX_STANDARD)
 
 linux_release_CFLAGS=-O2
 linux_release_CXXFLAGS=$(linux_release_CFLAGS)

depends/hosts/mingw32.mk

@@ -2,8 +2,8 @@ ifneq ($(shell $(SHELL) $(.SHELLFLAGS) "command -v $(host)-g++-posix"),)
 mingw32_CXX := $(host)-g++-posix
 endif
 
-mingw32_CFLAGS=-pipe
-mingw32_CXXFLAGS=$(mingw32_CFLAGS)
+mingw32_CFLAGS=-pipe -std=$(C_STANDARD)
+mingw32_CXXFLAGS=-pipe -std=$(CXX_STANDARD)
 
 mingw32_release_CFLAGS=-O2
 mingw32_release_CXXFLAGS=$(mingw32_release_CFLAGS)

depends/packages/boost.mk

@@ -28,7 +28,7 @@ ifneq (,$(findstring clang,$($(package)_cxx)))
 endif
 $(package)_archiver_$(host_os)=$($(package)_ar)
 $(package)_config_libraries=filesystem,system,thread,test,iostreams
-$(package)_cxxflags+=-std=c++17 -DBOOST_NO_CXX98_FUNCTION_BASE
+$(package)_cxxflags+=-DBOOST_NO_CXX98_FUNCTION_BASE
 $(package)_cxxflags_linux=-fPIC
 $(package)_cxxflags_android=-fPIC
 endef

depends/packages/openssl.mk

@@ -5,7 +5,8 @@ $(package)_file_name=OpenSSL_$(subst .,_,$($(package)_version)).tar.gz
 $(package)_sha256_hash=dac036669576e83e8523afdb3971582f8b5d33993a2d6a5af87daa035f529b4f
 
 define $(package)_set_vars
-$(package)_config_env=AR="$($(package)_ar)" RANLIB="$($(package)_ranlib)" CC="$($(package)_cc)"
+# OpenSSL relies on the asm keyword but that fails when it's not compiled with GNU extensions.
+$(package)_config_env=AR="$($(package)_ar)" RANLIB="$($(package)_ranlib)" CC="$($(package)_cc) -Dasm=__asm__"
 $(package)_config_opts=--prefix=$(host_prefix) --openssldir=$(host_prefix)/etc/openssl
 $(package)_config_opts+=no-camellia
 $(package)_config_opts+=no-capieng

depends/packages/qt.mk

@@ -39,7 +39,7 @@ $(package)_config_opts_release += -silent
 $(package)_config_opts_debug = -debug
 $(package)_config_opts_debug += -optimized-tools
 $(package)_config_opts += -bindir $(build_prefix)/bin
-$(package)_config_opts += -c++std c++17
+$(package)_config_opts += -c++std
 $(package)_config_opts += -confirm-license
 $(package)_config_opts += -hostprefix $(build_prefix)
 $(package)_config_opts += -no-compile-examples