Enable _GNU_SOURCE on Linux for POSIX/GNU extensions

Fixes CI failures: strdup, qsort_r, and clock_gettime are not declared
under strict -std=c11 on Linux without _GNU_SOURCE.

Author: farkasmark

Makefile

@@ -2,6 +2,12 @@ CC      ?= cc
 CFLAGS  = -O2 -Wall -Wextra -std=c11 -Iinclude
 LDFLAGS = -lm
 
+# On Linux, enable GNU extensions for strdup, qsort_r, clock_gettime, etc.
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Linux)
+CFLAGS += -D_GNU_SOURCE
+endif
+
 SRCS = src/platform.c src/gguf.c src/quant.c src/model.c \
        src/transformer.c src/tokenizer.c src/sampler.c src/main.c
 OBJS = $(SRCS:.c=.o)

src/platform.c

@@ -1,7 +1,3 @@
-#if defined(__linux__)
-#define _POSIX_C_SOURCE 200112L
-#endif
-
 #include "platform.h"
 #include <stdio.h>
 #include <stdlib.h>