[ci] use pre-compiled qemu-system-arm binary.

Author: sekineh

cortex-m-rt/.travis.yml

@@ -1,10 +1,5 @@
 language: rust
 
-addons:
-  apt:
-    packages:
-    - qemu-system-arm
-
 matrix:
   include:
     - env: TARGET=x86_64-unknown-linux-gnu
@@ -52,7 +47,7 @@ before_install: set -e
 
 install:
   - bash ci/install.sh
-  - export PATH="$PATH:$PWD/gcc/bin"
+  - export PATH="$PATH:$PWD/gcc/bin:$PWD/qemu"
 
 script:
   - bash ci/script.sh

cortex-m-rt/ci/install.sh

@@ -8,6 +8,10 @@ main() {
     mkdir gcc
 
     curl -L https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2?revision=bc2c96c0-14b5-4bb4-9f18-bceb4050fee7?product=GNU%20Arm%20Embedded%20Toolchain,64-bit,,Linux,7-2018-q2-update | tar --strip-components=1 -C gcc -xj
+
+    mkdir qemu
+    curl -L https://github.com/japaric/qemu-bin/raw/master/14.04/qemu-system-arm-2.12.0 > qemu/qemu-system-arm
+    chmod +x qemu/qemu-system-arm
 }
 
 main