Really set errno if __pthread_clone fails.

If r0 == 0, we're the child. If r0 > 0, we're the parent.
Otherwise set errno.

The __bionic_clone code I copy & pasted was wrong. This patch
fixes both.

Bug: 3461078
Change-Id: Ibb7d6cc7e54e666841f2f0dc59a141a0b31982e4
diff --git a/libc/arch-arm/bionic/clone.S b/libc/arch-arm/bionic/clone.S
index 6bd6bdf..39bd79d 100644
--- a/libc/arch-arm/bionic/clone.S
+++ b/libc/arch-arm/bionic/clone.S
@@ -47,7 +47,7 @@
 
     # In parent, reload saved registers then either exit or set errno.
     ldmfd   sp!, {r4, r7}
-    bxne    lr
+    bxpl    lr
     b       __set_syscall_errno
 
 1:  # The child.
@@ -96,7 +96,7 @@
 
     # In the parent, reload saved registers then either exit or set errno.
     ldmfd   sp!, {r4, r5, r6, r7}
-    bxne    lr
+    bxpl    lr
     b       __set_syscall_errno
 
 1:  # The child.