[llvm-readobj] Install llvm-readelf alias

Install an llvm-readelf symlink to llvm-readobj.
When invoked as *readelf*, default to -elf-output-style=GNU.

Patch by Roland McGrath

Differential Revision: https://reviews.llvm.org/D33869

llvm-svn: 308408
diff --git a/llvm/test/tools/llvm-readobj/gnu-sections.test b/llvm/test/tools/llvm-readobj/gnu-sections.test
index 1b04f0c..f5b504f 100644
--- a/llvm/test/tools/llvm-readobj/gnu-sections.test
+++ b/llvm/test/tools/llvm-readobj/gnu-sections.test
@@ -8,6 +8,8 @@
 RUN: llvm-readobj -W --sections \
 RUN:   %p/Inputs/relocs.obj.elf-x86_64 --elf-output-style=GNU \
 RUN:   | FileCheck %s -check-prefix ELF64
+RUN: llvm-readelf -W -S %p/Inputs/relocs.obj.elf-x86_64 \
+RUN:   | FileCheck %s -check-prefix ELF64
 
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