[Driver] Generate .eh_frame_hdr for static executables too.

[danalbert]

Summary

libgcc won't unwind without an .eh_frame_hdr section.

[srhines]

LGTM, but we should make sure that there are no objections, especially since there is no rationale for why this was present to begin with.

[chandlerc]

Agreed.

lib/Driver/ToolChains/Gnu.cpp

if (Arch == llvm::Triple::aarch64 && isAndroid) {
     std::string CPU = getCPUName(Args, Triple);
     if (CPU.empty() || CPU == "generic" || CPU == "cortex-a53")
       CmdArgs.push_back("--fix-cortex-a53-843419");
   }
 
   for (const auto &Opt : ToolChain.ExtraOpts)
     CmdArgs.push_back(Opt.c_str());
 
-  if (!Args.hasArg(options::OPT_static)) {
-    CmdArgs.push_back("--eh-frame-hdr");
-  }
 
   if (const char *LDMOption = getLDMOption(ToolChain.getTriple(), Args)) {
     CmdArgs.push_back("-m");
     CmdArgs.push_back(LDMOption);
   } else {
     D.Diag(diag::err_target_unknown_triple) << Triple.str();
     return;
   }

test/Driver/linux-ld.c

 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=x86_64-unknown-linux -rtlib=platform \
 // RUN:     -static \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-64-STATIC %s
 // CHECK-LD-64-STATIC-NOT: warning:
 // CHECK-LD-64-STATIC: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
-// CHECK-LD-64-STATIC-NOT: "--eh-frame-hdr"
+// CHECK-LD-64-STATIC: "--eh-frame-hdr"
 // CHECK-LD-64-STATIC: "-m" "elf_x86_64"
 // CHECK-LD-64-STATIC-NOT: "-dynamic-linker"
 // CHECK-LD-64-STATIC: "-static"
 // CHECK-LD-64-STATIC: "{{.*}}/usr/lib/gcc/x86_64-unknown-linux/4.6.0{{/|\\\\}}crtbeginT.o"
 // CHECK-LD-64-STATIC: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0"
 // CHECK-LD-64-STATIC: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib"
 // CHECK-LD-64-STATIC: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../.."
 // CHECK-LD-64-STATIC: "-L[[SYSROOT]]/lib"