[PPC] Fix PR24686 by failing assembly for an invalid relocation
PR24686 identifies a problem where a relocation expression is invalid
when not all of the symbols in the expression can be locally
resolved. This causes the compiler to request a PC-relative half16ds
relocation, which is nonsensical for PowerPC. This patch recognizes
this situation and ensures we fail the assembly cleanly.
Test case provided by Anton Blanchard.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251027
91177308-0d34-0410-b5e6-
96231b3b80d8