[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/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 7844b10..7f401aa 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -38,6 +38,7 @@
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Target/TargetOptions.h"
 #include <atomic>
 #include <memory>
 #include <sys/stat.h>
@@ -456,6 +457,20 @@
   Opts.DisableFree = Args.hasArg(OPT_disable_free);
   Opts.DisableTailCalls = Args.hasArg(OPT_mdisable_tail_calls);
   Opts.FloatABI = Args.getLastArgValue(OPT_mfloat_abi);
+  if (Arg *A = Args.getLastArg(OPT_meabi)) {
+    StringRef Value = A->getValue();
+    llvm::EABI EABIVersion = llvm::StringSwitch<llvm::EABI>(Value)
+                                 .Case("default", llvm::EABI::Default)
+                                 .Case("4", llvm::EABI::EABI4)
+                                 .Case("5", llvm::EABI::EABI5)
+                                 .Case("gnu", llvm::EABI::GNU)
+                                 .Default(llvm::EABI::Unknown);
+    if (EABIVersion == llvm::EABI::Unknown)
+      Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args)
+                                                << Value;
+    else
+      Opts.EABIVersion = Value;
+  }
   Opts.LessPreciseFPMAD = Args.hasArg(OPT_cl_mad_enable);
   Opts.LimitFloatPrecision = Args.getLastArgValue(OPT_mlimit_float_precision);
   Opts.NoInfsFPMath = (Args.hasArg(OPT_menable_no_infinities) ||