build: Prevent gensyms.sh from failing if pipefail is not supported by the shell

stage23/gensyms.sh

@@ -1,7 +1,8 @@
 #!/bin/sh
 
 set -e
-set -o pipefail || true
+
+./test_pipefail.sh && set -o pipefail
 
 TMP1=$(mktemp)
 TMP2=$(mktemp)

stage23/test_pipefail.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+set -e
+
+set -o pipefail 2>/dev/null