parallel-tests: work around Solaris XPG4 make segfault Issue exposed by test `posixsubst-tests-p.test', and similar to the problem solved by commit `v1.11-159-ge7aa360'. * lib/am/check.am [%?PARALLEL_TESTS%] (check-TESTS): Trim trailing whitespace from $list, to avoid triggering a nasty bug (potential segfault) on Solaris XPG4 make and Heirloom make.