[LibOS] Remove USE_clone_FOR_fork and glibc patch for fork

LibOS/Makefile

@@ -74,11 +74,6 @@ GLIBC_PATCHES = \
 	glibc-no-pie.patch \
 	glibc-liblibos.patch
 
-# USE_clone_FOR_fork = true
-ifneq ($(USE_clone_FOR_fork),)
-GLIBC_PATCHES += glibc-arch-fork.patch
-endif
-
 ifneq ($(filter %.gold,$(shell readlink -f /usr/bin/ld)),)
 GLIBC_PATCHES += glibc-ld.gold.patch
 endif

LibOS/glibc-arch-fork.patch

@@ -1,20 +0,0 @@
-diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/fork.c b/nptl/sysdeps/unix/sysv/linux/x86_64/fork.c
-index a036b92..40a1eaf 100644
---- a/nptl/sysdeps/unix/sysv/linux/x86_64/fork.c
-+++ b/nptl/sysdeps/unix/sysv/linux/x86_64/fork.c
-@@ -21,9 +21,12 @@
- #include <sysdep.h>
- #include <tls.h>
- 
- #define ARCH_FORK() \
--  INLINE_SYSCALL (clone, 4,						      \
--		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
--		  NULL, &THREAD_SELF->tid)
-+ ({ unsigned long ret = INLINE_SYSCALL (fork, 0);	\
-+    if (!ret) {						\
-+	pid_t pid = INLINE_SYSCALL (getpid, 0);		\
-+	THREAD_SETMEM (THREAD_SELF, pid, pid);		\
-+	THREAD_SETMEM (THREAD_SELF, tid, pid);		\
-+    } ret; })
- 
- #include "../fork.c"