[ASan] Not linking asan_static library for DSO.

[kstoimenov]

Summary

Without this change DSOs fail to link because of missing asan_report_(load|store)n functions.

[kda]

unit test?

clang/lib/Driver/ToolChains/CommonArgs.cpp

if (SanArgs.needsHwasanRt() && SanArgs.linkRuntimes()) {
         SharedRuntimes.push_back("hwasan");
     }
   }
 
   // The stats_client library is also statically linked into DSOs.
   if (SanArgs.needsStatsRt() && SanArgs.linkRuntimes())
     StaticRuntimes.push_back("stats_client");
 
-  // Always link the static runtime regardless of DSO or executable.
-  if (SanArgs.needsAsanRt())
-    HelperStaticRuntimes.push_back("asan_static");
-
   // Collect static runtimes.
   if (Args.hasArg(options::OPT_shared)) {
     // Don't link static runtimes into DSOs.
     return;
   }
 
+  // Always link the static runtime for executable.
+  if (SanArgs.needsAsanRt())
+    HelperStaticRuntimes.push_back("asan_static");
+
   // Each static runtime that has a DSO counterpart above is excluded below,
   // but runtimes that exist only as static are not affected by needsSharedRt.
 
   if (!SanArgs.needsSharedRt() && SanArgs.needsAsanRt() && SanArgs.linkRuntimes()) {
     StaticRuntimes.push_back("asan");
     if (SanArgs.linkCXXRuntimes())
       StaticRuntimes.push_back("asan_cxx");
   }