Looks like I don’t have xlclang installed:
ls /usr/vacpp/bin/xlc*
/usr/vacpp/bin/xlc@ /usr/vacpp/bin/xlc++@
/usr/vacpp/bin/xlc++128@ /usr/vacpp/bin/xlc++128_r@
/usr/vacpp/bin/xlc++128_r4@ /usr/vacpp/bin/xlc++128_r7@
/usr/vacpp/bin/xlc++128core@ /usr/vacpp/bin/xlc++128core_r@
/usr/vacpp/bin/xlc++128core_r7@ /usr/vacpp/bin/xlc++_r@
/usr/vacpp/bin/xlc++_r4@ /usr/vacpp/bin/xlc++_r7@
/usr/vacpp/bin/xlc++core@ /usr/vacpp/bin/xlc++core_r@
/usr/vacpp/bin/xlc++core_r7@ /usr/vacpp/bin/xlc128@
/usr/vacpp/bin/xlc128_r@ /usr/vacpp/bin/xlc128_r4@
/usr/vacpp/bin/xlc128_r7@ /usr/vacpp/bin/xlc_r@
/usr/vacpp/bin/xlc_r4@ /usr/vacpp/bin/xlc_r7@
Is it difficult to install xlclang?