Index: lld/COFF/DriverUtils.cpp
===================================================================
--- lld/COFF/DriverUtils.cpp
+++ lld/COFF/DriverUtils.cpp
@@ -22,6 +22,7 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/BinaryFormat/COFF.h"
+#include "llvm/Config/config.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Object/WindowsResource.h"
 #include "llvm/Option/Arg.h"
@@ -360,6 +361,7 @@
   return Ret;
 }
 
+#if LLVM_WIN_MANIFEST_ENABLED
 static Expected<std::unique_ptr<MemoryBuffer>>
 createManifestXmlWithInternalMt(std::string &DefaultXml) {
   std::unique_ptr<MemoryBuffer> DefaultXmlCopy =
@@ -372,20 +374,22 @@
   for (StringRef Filename : Config->ManifestInput) {
     std::unique_ptr<MemoryBuffer> Manifest =
         check(MemoryBuffer::getFile(Filename));
-    if (auto E = Merger.merge(*Manifest.get())) {
-      warn("internal manifest tool failed on file " + Filename);
-      return std::move(E);
-    }
+    if (auto E = Merger.merge(*Manifest.get()))
+      return make_error<windows_manifest::WindowsManifestError>(
+          "internal manifest tool failed on file " + Filename + ": " +
+          toString(std::move(E)));
   }
 
   return Merger.getMergedManifest();
 }
-
-static std::unique_ptr<MemoryBuffer>
+#else
+static Expected<std::unique_ptr<MemoryBuffer>>
 createManifestXmlWithExternalMt(std::string &DefaultXml) {
   const Triple HostTriple(Triple::normalize(LLVM_HOST_TRIPLE));
   if (!HostTriple.isOSWindows())
-    fatal("manifest ignored because no external manifest tool available");
+    return make_error<windows_manifest::WindowsManifestError>(
+        "external mt.exe is not available because this is not a Windows "
+        "system");
   // Create the default manifest file as a temporary file.
   TemporaryFile Default("defaultxml", "manifest");
   std::error_code EC;
@@ -412,28 +416,19 @@
 
   return check(MemoryBuffer::getFile(User.Path), "could not open " + User.Path);
 }
+#endif
 
 static std::string createManifestXml() {
   std::string DefaultXml = createDefaultXml();
   if (Config->ManifestInput.empty())
     return DefaultXml;
 
-  // If manifest files are supplied by the user using /MANIFESTINPUT
-  // option, we need to merge them with the default manifest. If libxml2
-  // is enabled, we may merge them with LLVM's own library.
-  Expected<std::unique_ptr<MemoryBuffer>> OutputBufferOrError =
-      createManifestXmlWithInternalMt(DefaultXml);
-  if (OutputBufferOrError)
-    return OutputBufferOrError.get()->getBuffer();
-  // Using built-in library failed, possibly because libxml2 is not installed.
-  // Shell out to mt.exe instead.
-  handleAllErrors(OutputBufferOrError.takeError(),
-                  [&](ErrorInfoBase &EIB) {
-                    warn("error with internal manifest tool: " + EIB.message());
-                  });
-  std::unique_ptr<MemoryBuffer> OutputBuffer;
-  OutputBuffer = createManifestXmlWithExternalMt(DefaultXml);
-  return OutputBuffer->getBuffer();
+#if LLVM_WIN_MANIFEST_ENABLED
+  auto OutputBuffer = check(createManifestXmlWithInternalMt(DefaultXml));
+#else
+  auto OutputBuffer = check(createManifestXmlWithExternalMt(DefaultXml));
+#endif
+  return OutputBuffer.get()->getBuffer();
 }
 
 static std::unique_ptr<MemoryBuffer>
Index: lld/test/COFF/manifestinput-error.test
===================================================================
--- /dev/null
+++ lld/test/COFF/manifestinput-error.test
@@ -0,0 +1,10 @@
+# UNSUPPORTED: manifest_tool
+# UNSUPPORTED: libxml2
+
+# RUN: yaml2obj %p/Inputs/ret42.yaml > %t.obj
+# RUN: not lld-link /out:%t.exe /entry:main \
+# RUN:   /manifest:embed \
+# RUN:   /manifestuac:"level='requireAdministrator'" \
+# RUN:   /manifestinput:%p/Inputs/manifestinput.test %t.obj 2>&1 | FileCheck %s
+
+# CHECK: error: external mt.exe is not available because this is not a Windows system
Index: lld/test/COFF/manifestinput-nowarning.test
===================================================================
--- /dev/null
+++ lld/test/COFF/manifestinput-nowarning.test
@@ -0,0 +1,11 @@
+# UNSUPPORTED: libxml2
+# REQUIRES: manifest_tool
+
+# RUN: yaml2obj %p/Inputs/ret42.yaml > %t.obj
+# RUN: lld-link /out:%t.exe /entry:main \
+# RUN:   /manifest:embed \
+# RUN:   /manifestuac:"level='requireAdministrator'" \
+# RUN:   /manifestinput:%p/Inputs/manifestinput.test %t.obj | \
+# RUN:	 FileCheck -allow-empty %s
+
+# CHECK-NOT: warning: error with internal manifest tool: no libxml2
Index: lld/test/lit.cfg
===================================================================
--- lld/test/lit.cfg
+++ lld/test/lit.cfg
@@ -270,3 +270,6 @@
 if (lit.util.which('cvtres', config.environment['PATH'])) or \
  (config.llvm_libxml2_enabled == "1"):
     config.available_features.add('manifest_tool')
+
+if (config.llvm_libxml2_enabled == "1"):
+    config.available_features.add('libxml2')
\ No newline at end of file
Index: llvm/include/llvm/Config/config.h.cmake
===================================================================
--- llvm/include/llvm/Config/config.h.cmake
+++ llvm/include/llvm/Config/config.h.cmake
@@ -386,6 +386,9 @@
 /* Define if libxml2 is supported on this platform. */
 #cmakedefine LLVM_LIBXML2_ENABLED ${LLVM_LIBXML2_ENABLED}
 
+/* Define if the manifest merging utility is available */
+#define LLVM_WIN_MANIFEST_ENABLED LLVM_LIBXML2_ENABLED
+
 /* Define to the extension used for shared libraries, say, ".so". */
 #cmakedefine LTDL_SHLIB_EXT "${LTDL_SHLIB_EXT}"