tsu: fix typo in tsu script

https://github.com/termux/termux-packages/issues/5256

packages/tsu/build.sh

@@ -2,6 +2,7 @@ TERMUX_PKG_HOMEPAGE=https://github.com/cswl/tsu
 TERMUX_PKG_DESCRIPTION="A su wrapper for Termux"
 TERMUX_PKG_LICENSE="ISC"
 TERMUX_PKG_VERSION=8.2.0
+TERMUX_PKG_REVISION=1
 TERMUX_PKG_PLATFORM_INDEPENDENT=true
 TERMUX_PKG_BUILD_IN_SRC=true
 TERMUX_PKG_SRCURL=(https://github.com/cswl/tsu/archive/v$TERMUX_PKG_VERSION.tar.gz)

packages/tsu/fix-typo.patch

@@ -0,0 +1,12 @@
+diff -uNr tsu-8.2.0/shell/tsu.sh tsu-8.2.0.mod/shell/tsu.sh
+--- tsu-8.2.0/shell/tsu.sh	2020-05-02 07:00:17.000000000 +0300
++++ tsu-8.2.0.mod/shell/tsu.sh	2020-05-07 18:22:24.320425132 +0300
+@@ -182,7 +182,7 @@
+ 	# Support for other shells.
+ 	# I dont have other shells to test
+ 	for SU_BINARY in '/su/bin/su' '/sbin/su' '/system/xbin/su' '/system/bin/su'; do
+-		if [ -e "$s" ]; then
++		if [ -e "$SU_BINARY" ]; then
+ 			# The --preserve-enivorment is used to copy variables
+ 			# Since we would have to detect busybox and others
+ 			exec "$SU_BINARY" -c "LD_PRELOAD=$LD_PRELOAD $STARTUP_SCRIPT"