Use DEBUG_POSTFIX instead of CMAKE_DEBUG_POSTFIX

CMAKE_DEBUG_POSTFIX is a global configuration parameter, and
changing it pollutes the configuration space for other projects
that enclose this project.

DEBUG_POSTFIX is better to use since it is a target-specific poperty.

Fixes #1334
Fixes #1268

googletest/CMakeLists.txt

@@ -27,8 +27,6 @@ option(
   "Build gtest with internal symbols hidden in shared libraries."
   OFF)
 
-set(CMAKE_DEBUG_POSTFIX "d" CACHE STRING "Generate debug library name with a postfix.")
-
 # Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
 include(cmake/hermetic_build.cmake OPTIONAL)
 

googletest/cmake/internal_utils.cmake

@@ -158,6 +158,10 @@ function(cxx_library_with_type name type cxx_flags)
   set_target_properties(${name}
     PROPERTIES
     COMPILE_FLAGS "${cxx_flags}")
+  # Generate debug library name with a postfix.
+  set_target_properties(${name}
+    PROPERTIES
+    DEBUG_POSTFIX "d")
   if (BUILD_SHARED_LIBS OR type STREQUAL "SHARED")
     set_target_properties(${name}
       PROPERTIES