I had never heard of GnuRoot before this thread, and I was already annoyed at the non-standard paths in Termux, so I decided to look at GnuRoot.
I downloaded GnuRoot at lunch yesterday, then discovered I needed GnuRoot Wheezy as well, then when I ran that it told me those two options were obsolete and I needed GnuRoot Debian, so I uninstalled the other two and downloaded that. Looked fine. I then did 'apt-get update' and got an error message. It turns out that my employer blocks the Debian sites, for some reason.
So yesterday evening I did 'apt-get update' and 'apt-get upgrade'; that took a while. Then I tried to wget the Gambit tgz file, but discovered neither wget nor curl is automatic with GnuRoot Debian, so I fetched both.
Then I downloaded Gambit, untarred, and did './configure'. But configure wasn't executable, so it didn't work. I said 'chmod 777 configure' but the execute bit still wasn't set. Searching Google I discovered that error occurs because the sd card is mounted noexec, but I don't have an sdcard, so I'm baffled.
Anyway, I did 'sh configure' and got an error message that gcc isn't installed. What kind of Debian is this? So I fetched gcc and did 'sh configure' again. I got another error message, I forget what.
So I gave up and went to bed.
I'll keep dealing with this over the next few days, and let you know when I make some progress.
Thanks to everyone who offered advice.
Phil