Revert "build: do not define _POSIX_C_SOURCE on NetBSD"

This reverts commit 5492145.

Author: 0-wiz-0

Makefile

@@ -1,7 +1,5 @@
 ifeq ($(OS),Windows_NT)
 $(error Windows is not supported)
-else
-	detected_OS := $(shell uname -s)
 endif
 
 VERSION := 0.25.1
@@ -29,10 +27,7 @@ OBJ := $(SRC:.c=.o)
 ARFLAGS := rcs
 CFLAGS ?= -O3 -Wall -Wextra -Wshadow -Wpedantic -Werror=incompatible-pointer-types
 override CFLAGS += -std=c11 -fPIC -fvisibility=hidden
-ifneq ($(detected_OS),NetBSD)
-override CFLAGS += -D_POSIX_C_SOURCE=200112L
-endif
-override CFLAGS += -D_DEFAULT_SOURCE
+override CFLAGS += -D_POSIX_C_SOURCE=200112L -D_DEFAULT_SOURCE
 override CFLAGS += -Ilib/src -Ilib/src/wasm -Ilib/include
 
 # ABI versioning