[Driver] TSan runtime now has a link-time dependency on libdispatch

Previously, the TSan runtime only required libdispatch on Darwin, which
required no explicit linker flags, because libdispatch is always
provided by the system (libSystem).

Now, the TSan runtime also has a link-time dependency on libdispatch on
Linux, where libdispatch (and the blocks runtime) is just another
library. We therefore need to specify them as additonal linker options.

Author: yln

lib/Driver/UnixToolChains.cpp

@@ -278,6 +278,12 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
   if (job.getKind() == LinkKind::Executable && context.OI.SelectedSanitizers) {
     Arguments.push_back(context.Args.MakeArgString(
         "-fsanitize=" + getSanitizerList(context.OI.SelectedSanitizers)));
+
+    // The TSan runtime depends on the blocks runtime and libdispatch.
+    if (context.OI.SelectedSanitizers & SanitizerKind::Thread) {
+      Arguments.push_back("-lBlocksRuntime");
+      Arguments.push_back("-ldispatch");
+    }
   }
 
   if (context.Args.hasArg(options::OPT_profile_generate)) {

test/Driver/sanitizers.swift

@@ -86,7 +86,7 @@
 // TSAN_watchOS_SIM: unsupported option '-sanitize=thread' for target 'i386-apple-watchos2.0'
 // TSAN_watchOS: unsupported option '-sanitize=thread' for target 'armv7k-apple-watchos2.0'
 // FUZZER_NONEXISTENT: unsupported option '-sanitize=fuzzer' for target 'x86_64-apple-macosx10.9'
-// TSAN_LINUX: -fsanitize=thread
+// TSAN_LINUX: -fsanitize=thread -lBlocksRuntime -ldispatch
 // TSAN_WINDOWS: unsupported option '-sanitize=thread' for target 'x86_64-unknown-windows-msvc'
 
 // TSAN: -rpath @executable_path