[EABI] Add Clang support for -meabi flag

The -meabi flag to control LLVM EABI version.

Without '-meabi' or with '-meabi default' imply LLVM triple default.
With '-meabi gnu' sets EABI GNU.
With '-meabi 4' or '-meabi 5' set EABI version 4 and 5 respectively.

A similar patch was introduced in LLVM.

Patch by Vinicius Tinti.

llvm-svn: 252463
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 03d4c6b..b415ea5 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3412,6 +3412,11 @@
     }
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_meabi)) {
+    CmdArgs.push_back("-meabi");
+    CmdArgs.push_back(A->getValue());
+  }
+
   CmdArgs.push_back("-mthread-model");
   if (Arg *A = Args.getLastArg(options::OPT_mthread_model))
     CmdArgs.push_back(A->getValue());