fix misalignment of dtv in static-linked programs with odd-sized TLS

both static and dynamic linked versions of the __copy_tls function
have a hidden assumption that the alignment of the beginning or end of
the memory passed is suitable for storing an array of pointers for the
dtv. pthread_create satisfies this requirement except when
libc.tls_size is misaligned, which cannot happen with dynamic linking
due to way update_tls_size computes the total size, but could happen
with static linking and odd-sized TLS.

src/env/__init_tls.c

@@ -95,7 +95,8 @@ void __init_tls(size_t *aux)
 	T.size += (-T.size - (uintptr_t)T.image) & (T.align-1);
 	if (T.align < MIN_TLS_ALIGN) T.align = MIN_TLS_ALIGN;
 
-	libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread);
+	libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread)
+		+ MIN_TLS_ALIGN-1 & -MIN_TLS_ALIGN;
 
 	if (libc.tls_size > sizeof builtin_tls) {
 #ifndef SYS_mmap2