`make linux` fails on linux

[bemasc]

When I run make linux, I see the following:

+ go build '--ldflags= -s -w -X main.version=v1.16.11' -o /build/electron-linux-amd64 ./
Cleaning up build environment...
INFO: Completed!
mv /home/bemasc/outline-go-tun2socks/build/linux/electron-linux-amd64 /home/bemasc/outline-go-tun2socks/build/linux/tun2socks
mv: cannot move '/home/bemasc/outline-go-tun2socks/build/linux/electron-linux-amd64' to '/home/bemasc/outline-go-tun2socks/build/linux/tun2socks': Permission denied
make: *** [Makefile:49: /home/bemasc/outline-go-tun2socks/build/linux/tun2socks] Error 1

ls shows that the binary has been built, but it is owned by root and is not writable by me:

$ ls -l build/linux/electron-linux-amd64 
-rwxr-xr-x 1 root root 3559872 Oct 25 12:37 build/linux/electron-linux-amd64

Presumably this is somehow because of the permissions settings on Docker.