Travis: Use GCC ARM Embedded PPA.

.travis.yml

@@ -13,12 +13,10 @@ notifications:
       # TODO: The "build_number.1" in this URL is almost certainly wrong, but correct value not available from Travis?
       - "Firmware download : https://portapack-h1-builds.s3.amazonaws.com/%{repository_slug}/%{build_number}/%{build_number}.1/build/firmware/portapack-h1-firmware-%{commit}.tar.bz2"
 
-before_script:
-  - wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/6-2017q2/gcc-arm-none-eabi-6-2017-q2-update-linux.tar.bz2 -O /tmp/gcc-arm.tar.bz2
-  - tar -xf /tmp/gcc-arm.tar.bz2
-  - export PATH=$PWD/gcc-arm-none-eabi-6-2017-q2-update/bin:$PATH
-  - export CC="arm-none-eabi-gcc"
-  - export CXX="arm-none-eabi-g++"
+before_install:
+  - sudo add-apt-repository ppa:team-gcc-arm-embedded/ppa -y
+  - sudo apt-get update -q
+  - sudo apt-get install gcc-arm-embedded -y
 
 script:
   # TODO: Introduce top-level Makefile, this is lame.