Remove obsolete CMake workaround

Author: pitrou

cpp/cmake_modules/SetupCxxFlags.cmake

@@ -235,24 +235,6 @@ if(WIN32)
     #   * https://developercommunity.visualstudio.com/content/problem/1249671/stdc17-generates-warning-compiling-windowsh.html
     set(CXX_COMMON_FLAGS "${CXX_COMMON_FLAGS} /wd5105")
 
-    if(ARROW_USE_CCACHE)
-      foreach(c_flag
-              CMAKE_CXX_FLAGS
-              CMAKE_CXX_FLAGS_RELEASE
-              CMAKE_CXX_FLAGS_DEBUG
-              CMAKE_CXX_FLAGS_MINSIZEREL
-              CMAKE_CXX_FLAGS_RELWITHDEBINFO
-              CMAKE_C_FLAGS
-              CMAKE_C_FLAGS_RELEASE
-              CMAKE_C_FLAGS_DEBUG
-              CMAKE_C_FLAGS_MINSIZEREL
-              CMAKE_C_FLAGS_RELWITHDEBINFO)
-        # ccache doesn't work with /Zi.
-        # See also: https://github.com/ccache/ccache/issues/1040
-        string(REPLACE "/Zi" "/Z7" ${c_flag} "${${c_flag}}")
-      endforeach()
-    endif()
-
     if(ARROW_USE_STATIC_CRT)
       foreach(c_flag
               CMAKE_CXX_FLAGS