[clang][Driver] Don't hardcode --as-needed/--no-as-needed on Illumos

`ninja check-all` currently fails on Illumos:

  [84/716] Generating default/Asan-i386-inline-Test
  FAILED: projects/compiler-rt/lib/asan/tests/default/Asan-i386-inline-Test
  cd /var/llvm/dist-amd64-release/projects/compiler-rt/lib/asan/tests && /var/llvm/dist-amd64-release/./bin/clang ASAN_INST_TEST_OBJECTS.gtest-all.cc.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_globals_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_interface_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_internal_interface_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_oob_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_mem_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_str_test.cpp.i386-inline.o ASAN_INST_TEST_OBJECTS.asan_test_main.cpp.i386-inline.o -o /var/llvm/dist-amd64-release/projects/compiler-rt/lib/asan/tests/default/./Asan-i386-inline-Test -g --driver-mode=g++ -fsanitize=address -m32
  ld: fatal: unrecognized option '--no-as-needed'
  ld: fatal: use the -z help option for usage information
  clang-11: error: linker command failed with exit code 1 (use -v to see invocation)

`clang` unconditionally passes `--as-needed`/`--no-as-needed` to the
linker.  This works on Solaris 11.[34] which added a couple of option
aliases to the native linker to improve compatibility with GNU `ld`.
Illumos `ld` didn't do this, so one needs to use the corresponding
native options `-z ignore`/`-z record` instead.

Because this works on both Solaris and Illumos, the current patch always
passes the native options on Solaris.  This isn't fully correct, however:
when using GNU `ld` on Solaris (not yet supported; I'm working on that),
one still needs `--as-needed` instead.

I'm hardcoding this decision because a generic detection via a `cmake` test
is hard: many systems have their own implementation of `getDefaultLinker`
and `cmake` would have to duplicate the information encoded there.
Besides, it would still break when `-fuse-ld` is used.

Tested on `amd64-pc-solaris2.11` (Solaris 11.4 and OpenIndiana 2020.04),
`sparcv9-sun-solaris2.11`, and `x86_64-pc-linux-gnu`.

Differential Revision: https://reviews.llvm.org/D84412

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -630,6 +630,16 @@ static bool addSanitizerDynamicList(const ToolChain &TC, const ArgList &Args,
   return false;
 }
 
+static const char *getAsNeededOption(const ToolChain &TC, bool as_needed) {
+  // While the Solaris 11.2 ld added --as-needed/--no-as-needed as aliases
+  // for the native forms -z ignore/-z record, they are missing in Illumos,
+  // so always use the native form.
+  if (TC.getTriple().isOSSolaris())
+    return as_needed ? "-zignore" : "-zrecord";
+  else
+    return as_needed ? "--as-needed" : "--no-as-needed";
+}
+
 void tools::linkSanitizerRuntimeDeps(const ToolChain &TC,
                                      ArgStringList &CmdArgs) {
   // Fuchsia never needs these.  Any sanitizer runtimes with system
@@ -639,7 +649,7 @@ void tools::linkSanitizerRuntimeDeps(const ToolChain &TC,
 
   // Force linking against the system libraries sanitizers depends on
   // (see PR15823 why this is necessary).
-  CmdArgs.push_back("--no-as-needed");
+  CmdArgs.push_back(getAsNeededOption(TC, false));
   // There's no libpthread or librt on RTEMS & Android.
   if (TC.getTriple().getOS() != llvm::Triple::RTEMS &&
       !TC.getTriple().isAndroid()) {
@@ -836,7 +846,7 @@ bool tools::addXRayRuntime(const ToolChain&TC, const ArgList &Args, ArgStringLis
 }
 
 void tools::linkXRayRuntimeDeps(const ToolChain &TC, ArgStringList &CmdArgs) {
-  CmdArgs.push_back("--no-as-needed");
+  CmdArgs.push_back(getAsNeededOption(TC, false));
   CmdArgs.push_back("-lpthread");
   if (!TC.getTriple().isOSOpenBSD())
     CmdArgs.push_back("-lrt");
@@ -1261,7 +1271,7 @@ static void AddUnwindLibrary(const ToolChain &TC, const Driver &D,
   bool AsNeeded = LGT == LibGccType::UnspecifiedLibGcc &&
                   !TC.getTriple().isAndroid() && !TC.getTriple().isOSCygMing();
   if (AsNeeded)
-    CmdArgs.push_back("--as-needed");
+    CmdArgs.push_back(getAsNeededOption(TC, true));
 
   switch (UNW) {
   case ToolChain::UNW_None:
@@ -1289,7 +1299,7 @@ static void AddUnwindLibrary(const ToolChain &TC, const Driver &D,
   }
 
   if (AsNeeded)
-    CmdArgs.push_back("--no-as-needed");
+    CmdArgs.push_back(getAsNeededOption(TC, false));
 }
 
 static void AddLibgcc(const ToolChain &TC, const Driver &D,