upgrade gcc-arm-none-eabi from the default 5.4.1 to 6.3.1 due to ARM runtime issues

Dockerfile

@@ -9,7 +9,6 @@ RUN apt-get update && apt-get install --no-install-recommends -y \
     dfu-programmer \
     dfu-util \
     gcc \
-    gcc-arm-none-eabi \
     gcc-avr \
     git \
     libnewlib-arm-none-eabi \
@@ -19,6 +18,10 @@ RUN apt-get update && apt-get install --no-install-recommends -y \
     zip \
     && rm -rf /var/lib/apt/lists/*
 
+# upgrade gcc-arm-none-eabi from the default 5.4.1 to 6.3.1 due to ARM runtime issues
+RUN wget -q https://developer.arm.com/-/media/Files/downloads/gnu-rm/6-2017q2/gcc-arm-none-eabi-6-2017-q2-update-linux.tar.bz2 -O - | \
+    tar xj --strip-components=1 -C /
+
 VOLUME /qmk_firmware
 WORKDIR /qmk_firmware
 COPY . .