[ARM] Incorrect relocation type for Thumb2 B<cond>.w

The Thumb2 conditional branch B<cond>.W has a different encoding (T3) 
to the unconditional branch B.W (T4) as it needs to record <cond>. 
As the encoding is different the B<cond>.W is given a different 
relocation type. 

ELF for the ARM Architecture 4.6.1.6 (Table-13) states that 
R_ARM_THM_JUMP19 should be used for B<cond>.W. At present the 
MC layer is using the R_ARM_THM_JUMP24 from B.W.

This change makes B<cond>.W use R_ARM_THM_JUMP19 and alters the 
existing test that checks for R_ARM_THM_JUMP24 to expect 
R_ARM_THM_JUMP19.

llvm-svn: 271997
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index d618df4..4118fe8 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -123,6 +123,8 @@
       Type = ELF::R_ARM_JUMP24;
       break;
     case ARM::fixup_t2_condbranch:
+      Type = ELF::R_ARM_THM_JUMP19;
+      break;
     case ARM::fixup_t2_uncondbranch:
       Type = ELF::R_ARM_THM_JUMP24;
       break;