Update the build script for debian.

durio/build.sh

@@ -1,16 +1,21 @@
 #!/usr/bin/env bash
 # To setup cross build on a linux machine, do the following
 # 1. Install package arm-linux-gnu-gcc (yum) or gcc-arm-linux-gnueabihf (apt).
+# 5. Install build-essential (apt only).
 # 2. Run `rustup target add armv7-unknown-linux-musleabihf`
 # 1. Add the following to ~/.cargo/config
 # [target.armv7-unknown-linux-musleabihf]
-# linker = "arm-linux-gnu-gcc"
+# linker = "arm-linux-gnu-gcc" (yum)
+# linker = "arm-linux-gnueabihf-gcc" (apt)
+# 4. Install rsync.
 
 set -ex
-rsync -av /Users/ditsing/Code/ruaft ec2:~/compile/ --exclude 'ruaft/target' --exclude 'ruaft/.git' --exclude '.idea'
-ssh ec2 'cd ~/compile/ruaft/durio && cargo build --target=armv7-unknown-linux-musleabihf --release'
+
+MACHINE=gcloud
+rsync -av /Users/ditsing/Code/ruaft $MACHINE:~/compile/ --exclude 'ruaft/target' --exclude 'ruaft/.git' --exclude '.idea'
+ssh $MACHINE 'cd ~/compile/ruaft/durio && cargo build --target=armv7-unknown-linux-musleabihf --release'
 mkdir -p /tmp/ruaft
-rsync -av 'ec2:~/compile/ruaft/target/armv7-unknown-linux-musleabihf/release/durio' '/tmp/ruaft/durio'
+rsync -av $MACHINE:'~/compile/ruaft/target/armv7-unknown-linux-musleabihf/release/durio' '/tmp/ruaft/durio'
 
 ssh alice 'pkill -9 durio || echo nothing'
 rsync -av '/tmp/ruaft/durio' alice:/tmp/durio