Update ci/verify-build.sh

Co-authored-by: Alan Somers <[email protected]>

Author: tgross35

ci/verify-build.sh

@@ -76,7 +76,7 @@ test_target() {
         nightly-*freebsd*) do_freebsd_checks=1 ;;
     esac
 
-    if [ "${do_freebsd_checks:-}" = "1" ]; then
+    if [ -n "$do_freebsd_checks" ]; then
         for version in $freebsd_versions; do
             export RUST_LIBC_UNSTABLE_FREEBSD_VERSION="$version"
             $cmd