testsuite: skip pr118817 over unmet hostedlib needs

testsuite: skip pr118817 over unmet hostedlib needs

The test for -shared support doesn't fail on riscv64-elf, unlike other
barebones targets including riscv32-elf (testing with -fpic -shared
overflows HI20 relocs) that don't enable a hosted libstdc++.

This test thus got skipped on those other platforms, but we still
gave it a shot on riscv64-elf, and then it failed because libstdc++
doesn't have all the headers enabled that the test requires.

Require hostedlib.

for  gcc/testsuite/ChangeLog

	* g++.dg/lto/pr118817_0.C: Require hostedlib.