Fix unresolved in gcc.dg/pr46932.c

Build only if pre-increment is supported.  Given there is no config test,
add a list of targets which have HAVE_PRE_INCREMENT set.

    testsuite/
	PR middle-end/46932
	* gcc.dg/pr46932.c: Compile on targets with pre-increment.

From-SVN: r250918

gcc/testsuite/ChangeLog

+2017-08-07  Wilco Dijkstra  <wdijkstr@arm.com>
+
+	PR middle-end/46932
+	* gcc.dg/pr46932.c: Compile on targets with pre-increment.
+
 2017-08-07  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* gcc.target/i386/pr81736-1.c: Removed.

gcc/testsuite/gcc.dg/pr46932.c

 /* { dg-options "-O2 -fdump-rtl-auto_inc_dec" } */
 
+/* Build on targets which have pre increment.  */
+/* { dg-do compile { target aarch64*-*-* arm*-*-* rs6000-*-* powerpc*-*-* arc*-*-* m32r-*-* tic6x-*-* } } */
+
 /* Check that accesses based on the frame pointer do not
    use auto increment.  */