Install runtime dlls in the INSTALL_DIR/bin directory. NFC

[sgundapa]

Summary

One of the earlier patches updated the cmake rule to install the
runtime dlls in INSTALL_DIR/lib which is not correct. This patch
updates the rule to install CMake's RUNTIME in bin directory

[beanz]

LGTM.

llvm/trunk/cmake/modules/AddLLVM.cmake

else()
     set(_is_gtest FALSE)
     set_property( GLOBAL APPEND PROPERTY LLVM_LIBS ${name} )
   endif()
 
   if( EXCLUDE_FROM_ALL )
     set_target_properties( ${name} PROPERTIES EXCLUDE_FROM_ALL ON)
   elseif(NOT _is_gtest)
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY OR ${name} STREQUAL "LTO")
+      set(install_dir lib${LLVM_LIBDIR_SUFFIX})
       if(ARG_SHARED OR BUILD_SHARED_LIBS)
-        if(WIN32 OR CYGWIN)
+        if(WIN32 OR CYGWIN OR MINGW)
           set(install_type RUNTIME)
+          set(install_dir bin)
         else()
           set(install_type LIBRARY)
         endif()
       else()
         set(install_type ARCHIVE)
       endif()
 
       install(TARGETS ${name}
             EXPORT LLVMExports
-            ${install_type} DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+            ${install_type} DESTINATION ${install_dir}
             COMPONENT ${name})
 
       if (NOT CMAKE_CONFIGURATION_TYPES)
         add_custom_target(install-${name}
                           DEPENDS ${name}
                           COMMAND "${CMAKE_COMMAND}"
                                   -DCMAKE_INSTALL_COMPONENT=${name}
                                   -P "${CMAKE_BINARY_DIR}/cmake_install.cmake")