Makefiles: Add noexecstack Options to Compilation and Linking

Hopefully this marks the binary artifacts `noexecstack` even on platforms
where binaries default to true.

lib/Makefile

@@ -25,6 +25,7 @@ ifeq ($(ZSTD_LIB_DECOMPRESSION), 0)
   ZSTD_LIB_DEPRECATED = 0
 endif
 
+
 include libzstd.mk
 
 ZSTD_FILES := $(ZSTD_COMMON_FILES) $(ZSTD_LEGACY_FILES)

lib/libzstd.mk

@@ -34,6 +34,8 @@ ZSTD_NO_ASM ?= 0
 # libzstd helpers
 ##################################################################
 
+VOID ?= /dev/null
+
 # Make 4.3 doesn't support '\#' anymore (https://lwn.net/Articles/810071/)
 NUM_SYMBOL := \#
 
@@ -59,6 +61,28 @@ LIBVER := $(shell echo $(LIBVER_SCRIPT))
 CCVER := $(shell $(CC) --version)
 ZSTD_VERSION?= $(LIBVER)
 
+
+ifndef ALREADY_APPENDED_NOEXECSTACK
+export ALREADY_APPENDED_NOEXECSTACK := 1
+ifeq ($(shell echo "int main(int argc, char* argv[]) { (void)argc; (void)argv; return 0; }" | $(CC) -z noexecstack -x c -Werror - -o $(VOID) 2>$(VOID) && echo 1 || echo 0),1)
+$(info Supports noexecstack linker flag!)
+$(info $(LDFLAGS))
+LDFLAGS += -z noexecstack
+$(info $(LDFLAGS))
+else
+$(info Doesn't support noexecstack linker flag!)
+endif
+ifeq ($(shell echo | $(CC) -Wa,--noexecstack -x assembler -Werror -c - -o $(VOID) 2>$(VOID) && echo 1 || echo 0),1)
+$(info Supports noexecstack assembler flag!)
+$(info $(CFLAGS))
+CFLAGS += -Wa,--noexecstack
+$(info $(CFLAGS))
+else
+$(info Doesn't support noexecstack assembler flag!)
+endif
+endif
+
+
 # ZSTD_LIB_MINIFY is a helper variable that
 # configures a bunch of other variables to space-optimized defaults.
 ZSTD_LIB_MINIFY ?= 0

programs/Makefile

@@ -62,8 +62,6 @@ else
   EXT =
 endif
 
-VOID = /dev/null
-
 # thread detection
 NO_THREAD_MSG := ==> no threads, building without multithreading support
 HAVE_PTHREAD := $(shell printf '$(NUM_SYMBOL)include <pthread.h>\nint main(void) { return 0; }' > have_pthread.c && $(CC) $(FLAGS) -o have_pthread$(EXT) have_pthread.c -pthread 2> $(VOID) && rm have_pthread$(EXT) && echo 1 || echo 0; rm have_pthread.c)