Require pthread effective target for test case using -pthread option.

2020-04-08  Sandra Loosemore  <sandra@codesourcery.com>

	gcc/testsuite/
	* g++.dg/tree-ssa/pr93940.C: Require pthread target.

gcc/testsuite/ChangeLog

+2020-04-08  Sandra Loosemore  <sandra@codesourcery.com>
+
+	* g++.dg/tree-ssa/pr93940.C: Require pthread target.
+
 2020-04-09  Kewen Lin  <linkw@gcc.gnu.org>
 
 	PR testsuite/94079

gcc/testsuite/g++.dg/tree-ssa/pr93940.C

 /* { dg-do compile } */
+/* { dg-require-effective-target pthread } */
 /* { dg-options "-Og --coverage -pthread -fdump-tree-optimized -std=c++17" } */
 using uint16_t = unsigned short;