fix link library name in cmake (PR microsoft#1114 by @WildCard65)

Author: daanx

CMakeLists.txt

@@ -473,10 +473,10 @@ function(find_link_library libname outlibname)
     message(VERBOSE "link library: -l${libname}")
     set(${outlibname} ${libname} PARENT_SCOPE)
   else()
-    find_library(MI_LIBPATH libname)
-    if (MI_LIBPATH)
-      message(VERBOSE "link library ${libname} at ${MI_LIBPATH}")
-      set(${outlibname} ${MI_LIBPATH} PARENT_SCOPE)
+    find_library(MI_LIBPATH_${libname} ${libname})
+    if (MI_LIBPATH_${libname})
+      message(VERBOSE "link library ${libname} at ${MI_LIBPATH_${libname}}")
+      set(${outlibname} ${MI_LIBPATH_${libname}} PARENT_SCOPE)
     else()
       message(VERBOSE "link library not found: ${libname}")
       set(${outlibname} "" PARENT_SCOPE)