always install arm-none-eabi-gcc

Author: japaric

cortex-m-rt/ci/install.sh

@@ -3,13 +3,11 @@ set -euxo pipefail
 main() {
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
         rustup target add $TARGET
+    fi
 
-        if [ ${CC:-gcc} = gcc ]; then
-            mkdir gcc
+    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
-        fi
-    fi
+    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
 }
 
 main