jenkins_arm.sh: disable external tests

We don not run 'make check' at all so configuring with external tests support is pointless.

Related: OS#5671
Change-Id: If96756a85ab3b01a786838a4882884efe33f968b
diff --git a/contrib/jenkins_arm.sh b/contrib/jenkins_arm.sh
index e7df37d..8793415 100755
--- a/contrib/jenkins_arm.sh
+++ b/contrib/jenkins_arm.sh
@@ -21,7 +21,6 @@
 	--disable-libsctp \
 	--disable-libusb \
 	--disable-libmnl \
-	--enable-external-tests \
 	CFLAGS="-Os -ffunction-sections -fdata-sections -nostartfiles -nodefaultlibs $WERROR_FLAGS"
 
     $MAKE $PARALLEL_MAKE