Fix printchplbuilds test for comm=none (#26403)

Fixes the recently added printchplbuilds test for comm=none builds. The
test had been written in an environment where there was more than one
Chapel runtime build, which changed the output of the test.

This PR also adds a skipif for having more than one runtime build to
prevent this issue

[Reviewed by @jhh67]

test/chplenv/printchplbuilds/printchplbuilds-print1.prediff

@@ -36,8 +36,8 @@ chpl_vars = [
     ("CHPL_TARGET_CPU", None),
     ("CHPL_LOCALE_MODEL", None),
     ("CHPL_COMM", None),
-    ("CHPL_COMM_SUBSTRATE", None),
-    ("CHPL_GASNET_SEGMENT", None),
+    ("CHPL_COMM_SUBSTRATE", None, lambda env: env["CHPL_COMM"] == "gasnet"),
+    ("CHPL_GASNET_SEGMENT", None, lambda env: env["CHPL_COMM"] == "gasnet"),
     ("CHPL_LIBFABRIC", None, lambda env: env["CHPL_COMM"] == "ofi"),
     ("CHPL_COMM_OFI_OOB", None, lambda env: env["CHPL_COMM"] == "ofi"),
     ("CHPL_TASKS", None),

test/chplenv/printchplbuilds/printchplbuilds-print1.skipif

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+# skip if printchplbuilds finds more than 1 build
+# this messes up the parsing in the prediff
+chpl_python=$($CHPL_HOME/util/config/find-python.sh)
+printchplbuilds=$CHPL_HOME/util/chplenv/printchplbuilds.py
+
+if $chpl_python $printchplbuilds --bash 1 &>/dev/null; then
+  echo True
+else
+  echo False
+fi