force travis to use 4-* (4-8-2014q2-0precise9 or newer) gcc-arm-none-eabi due to a bug not

installing the c++ headers when installing the stock cross-compiler

.travis.yml

@@ -17,7 +17,8 @@ before_install:
 install:
     - sudo apt-get install build-essential
     - sudo apt-get install gcc-multilib
-    - sudo apt-get install gcc-arm-none-eabi
+#TODO: remove the `=4-*` if the stock gcc-arm-none-eabi ships the missing c++ headers (cf. #1656)
+    - sudo apt-get install gcc-arm-none-eabi=4-*
     - sudo apt-get install gcc-msp430
     - sudo apt-get install pcregrep libpcre3
     - sudo apt-get install qemu-system-x86 python3