re PR c++/64527 (Constructor for empty struct not called in some situations)

Fix PR c++/64527

gcc/
	PR c++/64527
	* gimplify.c (gimplify_init_constructor): Always emit a
	side-effecting constructor.

gcc/testsuite/
	PR c++/64527
	* g++.dg/init/pr64527.C: New test.

From-SVN: r222176