Add host-specific include for getpid() in FrontendTool.

Author: artemcm

lib/Basic/ParseableOutput.cpp

@@ -79,11 +79,6 @@ namespace {
 
 Action::Kind
 mapFrontendInvocationToActionKind(const CompilerInvocation &Invocation) {
-  auto Executable = llvm::sys::path::filename(
-      Invocation.getFrontendOptions().MainExecutablePath);
-  assert(Executable.str() == "swift-frontend" &&
-         "Expected a swift-frontend invocation.");
-
   Action::Kind ActionKind;
   FrontendOptions::ActionType ActionType =
       Invocation.getFrontendOptions().RequestedAction;

lib/FrontendTool/FrontendTool.cpp

@@ -79,6 +79,11 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 
+#if __has_include(<unistd.h>)
+#include <unistd.h>
+#elif defined(_WIN32)
+#include <process.h>
+#endif
 #include <algorithm>
 #include <memory>
 #include <unordered_set>