Convert a few assert failures into proper errors.

Fixes PR25944.

llvm-svn: 257697
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index 52eba8b..388ce799 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -34,8 +34,8 @@
 
     ~ARMELFObjectWriter() override;
 
-    unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
-                          bool IsPCRel) const override;
+    unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                          const MCFixup &Fixup, bool IsPCRel) const override;
 
     bool needsRelocateWithSymbol(const MCSymbol &Sym,
                                  unsigned Type) const override;
@@ -67,7 +67,7 @@
 // Need to examine the Fixup when determining whether to 
 // emit the relocation as an explicit symbol or as a section relative
 // offset
-unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
+unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
                                           const MCFixup &Fixup,
                                           bool IsPCRel) const {
   return GetRelocTypeInner(Target, Fixup, IsPCRel);