Makefile.rtl (x86_64-vx7r2) adds a package i-vxinco.adb, which imports
a variable that is not exported on rtp. This problem only shows up
with a shared library runtime because it's never actually used, and
gets optimized away in a static link.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* Makefile.rtl (x86_64-vx7r2) [EXTRA_GNATRTL_TASKING_OBJS]: Move
	i-vxinco.o out of RTP runtime.