[aarch64-port-dev ] Add missing export

[Edward Nevill]

Add missing export in cross_compile

Ed.

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exporting patch:
# HG changeset patch
# User Edward Nevill edward.nevill at linaro.org
# Date 1380660897 -3600
#      Tue Oct 01 21:54:57 2013 +0100
# Node ID 60ddcc7923e7a386c2927da27bd0f7a65e960ca8
# Parent  c4e0096dad572325713409d06f19786504d7c51a
Export ALT_SDT_H

diff -r c4e0096dad57 -r 60ddcc7923e7 cross_compile
--- a/cross_compile	Fri Sep 27 15:49:31 2013 +0100
+++ b/cross_compile	Tue Oct 01 21:54:57 2013 +0100
@@ -8,5 +8,5 @@
 	fi
 mkdir -p /tmp/oe_45434e/jenkins-setup/build/tmp-eglibc
 ln -f -s $IWD/sysroots /tmp/oe_45434e/jenkins-setup/build/tmp-eglibc/
-ALT_SDT_H=$IWD/sysroots/genericarmv8/usr/include/sys/sdt.h
+export ALT_SDT_H=$IWD/sysroots/genericarmv8/usr/include/sys/sdt.h
 make STRIP_POLICY=no_strip POST_STRIP_CMD="" images
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