fix: stop suppressing errexit for the whole install

POSIX ignores -e for every command of an AND-OR list but the last, and that
suppression covers the entire body of a function called there. So `main "$@" ||
exit 1` disabled set -e for the whole script: tar, mkdir, chmod and mv could
all fail unnoticed. Reinstalling over an existing binary with a corrupt archive
printed the success message and exited 0.

The idiom came from rustup and cargo-dist, which set -u only and wrap every
command in `ensure`, so the trailing `|| exit 1` costs them nothing. It is not
transferable to a script that relies on -e.

beep boop

Author: khvn26

install.sh

@@ -267,4 +267,4 @@ If ${VERSION} was released moments ago its archives may still be uploading — r
 	fi
 }
 
-main "$@" || exit 1
+main "$@"