Download srecord for arm aapcs tests

.travis.yml

@@ -41,10 +41,11 @@ before_script:
 
   ## Install mainline ARM toolchain.  gcc-arm-none-eabi is available
   ## in Ubuntu >= 14.04, but this external PPA is needed for 12.04.
+  ## Install srecord
   - if [ ${BUILD_ARCH:-0} = arm-aapcs ] ; then
       sudo add-apt-repository -y ppa:terry.guo/gcc-arm-embedded &&
       sudo apt-get -qq update &&
-      sudo apt-get -qq install gcc-arm-none-eabi &&
+      sudo apt-get -qq install gcc-arm-none-eabi srecord &&
       arm-none-eabi-gcc --version ;
     fi