link libjpeg against DLL version of mscvrt library

makefile.vc builds libjpeg static with /MT flags that
link with static mscvt. This libjpeg when linking against
gdal throws link error as gdal is linked against MSVCRT
dll version so as all other dependencies in superbuild.
This makes external libjpeg currently unusabe with gdal
and end upwith two libjpeg in the build. This commit
build libjpeg as cmake project which automatically add /MD
depending on configuration and finally to have a single libjpeg
used in GDAL and libtiff

http://dash.orfeo-toolbox.org/testDetails.php?test=28153014&build=170814

CMake/External_jpeg.cmake

@@ -15,43 +15,27 @@ else()
   set(JPEG_SB_SRC ${CMAKE_BINARY_DIR}/${proj}/src/${proj})
   
   if(WIN32)
-
-   
-   ExternalProject_Add(${proj}_build
+      
+    ExternalProject_Add(${proj}
       PREFIX ${proj}
       URL "http://www.ijg.org/files/jpegsr8c.zip"
       URL_MD5 2af71a567af8f60a649b2fcc87c88192
       SOURCE_DIR ${JPEG_SB_SRC}
       BINARY_DIR ${JPEG_SB_BUILD_DIR}
       INSTALL_DIR ${CMAKE_INSTALL_PREFIX}
-      PATCH_COMMAND ${CMAKE_COMMAND} -E copy_directory ${JPEG_SB_SRC} ${JPEG_SB_BUILD_DIR}
-      CONFIGURE_COMMAND ""
-      BUILD_COMMAND nmake /f ${JPEG_SB_BUILD_DIR}/makefile.vc nodebug=1
-      INSTALL_COMMAND ${CMAKE_COMMAND} -E copy  ${CMAKE_SOURCE_DIR}/patches/${proj}/CMakeLists.txt
-      ${CMAKE_BINARY_DIR}/${proj}/_install
-    )
-
-    ExternalProject_Add_Step(${proj}_build copy_jconfig
-      COMMAND ${CMAKE_COMMAND} -E copy 
-        ${JPEG_SB_BUILD_DIR}/jconfig.vc ${JPEG_SB_BUILD_DIR}/jconfig.h
-      DEPENDEES configure
-      DEPENDERS build
-    )
-      
-      
-    ExternalProject_Add(${proj}
-      PREFIX ${proj}/_install
-      DOWNLOAD_COMMAND ""
-      SOURCE_DIR ${proj}/_install
-      BINARY_DIR ${JPEG_SB_BUILD_DIR}
-      INSTALL_DIR ${CMAKE_INSTALL_PREFIX}
+      PATCH_COMMAND ${CMAKE_COMMAND} -E copy  ${CMAKE_SOURCE_DIR}/patches/${proj}/CMakeLists.txt ${JPEG_SB_SRC}
       CMAKE_CACHE_ARGS
         -DCMAKE_INSTALL_PREFIX:STRING=${CMAKE_INSTALL_PREFIX}
         -DCMAKE_BUILD_TYPE:STRING=Release
-        -DJPEG_BUILD_DIR:STRING=${JPEG_SB_BUILD_DIR}
-      DEPENDS ${proj}_build
-      CMAKE_COMMAND
+        -DCMAKE_VERBOSE_MAKEFILE:BOOL=OFF
     )
+
+    ExternalProject_Add_Step(${proj} copy_jconfig
+      COMMAND ${CMAKE_COMMAND} -E copy 
+        ${JPEG_SB_SRC}/jconfig.vc ${JPEG_SB_SRC}/jconfig.h
+      DEPENDEES patch
+      DEPENDERS build
+    )        
       
 
   else()