Support bfdname "elf32-hexagon".

Add support and update testcases.

Differential Revision: https://reviews.llvm.org/D77579
diff --git a/llvm/tools/llvm-objcopy/CopyConfig.cpp b/llvm/tools/llvm-objcopy/CopyConfig.cpp
index 69d6180..df2fbbb 100644
--- a/llvm/tools/llvm-objcopy/CopyConfig.cpp
+++ b/llvm/tools/llvm-objcopy/CopyConfig.cpp
@@ -273,6 +273,7 @@
     // SPARC
     {"elf32-sparc", {ELF::EM_SPARC, false, false}},
     {"elf32-sparcel", {ELF::EM_SPARC, false, true}},
+    {"elf32-hexagon", {ELF::EM_HEXAGON, false, true}},
 };
 
 static Expected<TargetInfo>