openssh: Replace some link(2) with rename(2)

OpenSSH uses a link to take a backup while replacing the known_hosts
file:

(1) link known_hosts to known_hosts.old
(2) move new file to known_hosts (overwriting the link there)

Since links are not allowed we replace link with rename:

(1) rename known_hosts to known_hosts.old
(2) move new file to known_hosts

This means that there is a window between (1) and (2) where the
known_hosts file is not available, but that is a really short window
and is hopefully acceptable here.

Fixes #2909.

packages/openssh/build.sh

@@ -1,7 +1,7 @@
 TERMUX_PKG_HOMEPAGE=https://www.openssh.com/
 TERMUX_PKG_DESCRIPTION="Secure shell for logging into a remote machine"
 TERMUX_PKG_VERSION=7.8p1
-TERMUX_PKG_REVISION=2
+TERMUX_PKG_REVISION=3
 TERMUX_PKG_SHA256=1a484bb15152c183bb2514e112aa30dd34138c3cfb032eee5490a66c507144ca
 TERMUX_PKG_SRCURL=https://fastly.cdn.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-${TERMUX_PKG_VERSION}.tar.gz
 TERMUX_PKG_DEPENDS="libandroid-support, ldns, openssl, libedit, libutil"

packages/openssh/hostfile.c.patch

@@ -0,0 +1,15 @@
+diff -u -r ../openssh-7.8p1/hostfile.c ./hostfile.c
+--- ../openssh-7.8p1/hostfile.c	2018-08-23 05:41:42.000000000 +0000
++++ ./hostfile.c	2018-09-29 08:21:44.261152558 +0000
+@@ -603,7 +603,11 @@
+ 			r = SSH_ERR_SYSTEM_ERROR;
+ 			goto fail;
+ 		}
++#ifdef __ANDROID__
++		if (rename(filename, back) == -1) {
++#else
+ 		if (link(filename, back) == -1) {
++#endif
+ 			oerrno = errno;
+ 			error("%s: link %.100s to %.100s: %s", __func__,
+ 			    filename, back, strerror(errno));

packages/openssh/ssh-keygen.c.patch

@@ -0,0 +1,15 @@
+diff -u -r ../openssh-7.8p1/ssh-keygen.c ./ssh-keygen.c
+--- ../openssh-7.8p1/ssh-keygen.c	2018-08-23 05:41:42.000000000 +0000
++++ ./ssh-keygen.c	2018-09-29 08:34:27.584063901 +0000
+@@ -1289,7 +1347,11 @@
+ 		/* Backup existing file */
+ 		if (unlink(old) == -1 && errno != ENOENT)
+ 			fatal("unlink %.100s: %s", old, strerror(errno));
++#ifdef __ANDROID__
++		if (rename(identity_file, old) == -1)
++#else
+ 		if (link(identity_file, old) == -1)
++#endif
+ 			fatal("link %.100s to %.100s: %s", identity_file, old,
+ 			    strerror(errno));
+ 		/* Move new one into place */