Add GNU/Hurd build support.

Note: this is not an officially supported target.
Contributed by Pino Toscano and Samuel Thibault. #1383 #1384

src/Makefile

@@ -357,6 +357,9 @@ else
   ifeq (GNU/kFreeBSD,$(TARGET_SYS))
     TARGET_XLIBS+= -ldl
   endif
+  ifeq (GNU,$(TARGET_SYS))
+    TARGET_XLIBS+= -ldl
+  endif
 endif
 endif
 endif

src/lj_arch.h

@@ -96,6 +96,9 @@
 #elif defined(__QNX__)
 #define LJ_TARGET_QNX		1
 #define LUAJIT_OS	LUAJIT_OS_POSIX
+#elif defined(__GNU__)
+#define LJ_TARGET_HURD		1
+#define LUAJIT_OS	LUAJIT_OS_POSIX
 #else
 #define LUAJIT_OS	LUAJIT_OS_OTHER
 #endif

src/lj_prng.c

@@ -125,7 +125,7 @@ static PRGR libfunc_rgr;
 #if __MAC_OS_X_VERSION_MIN_REQUIRED >= 101200
 #define LJ_TARGET_HAS_GETENTROPY	1
 #endif
-#elif (LJ_TARGET_BSD && !defined(__NetBSD__)) || LJ_TARGET_SOLARIS || LJ_TARGET_CYGWIN || LJ_TARGET_QNX
+#elif (LJ_TARGET_BSD && !defined(__NetBSD__)) || LJ_TARGET_SOLARIS || LJ_TARGET_CYGWIN || LJ_TARGET_QNX || LJ_TARGET_HURD
 #define LJ_TARGET_HAS_GETENTROPY	1
 #endif