Set VCPKG_ROOT

Signed-off-by: Guian Gumpac <guian.gumpac@improving.com>

Author: GumpacG

build_win64.bat

@@ -23,6 +23,7 @@ if NOT DEFINED ARROW_GIT_REPOSITORY SET ARROW_GIT_REPOSITORY="https://github.com
 if NOT DEFINED ARROW_GIT_TAG SET ARROW_GIT_TAG="b050bd0d31db6412256cec3362c0d57c9732e1f2"
 if NOT DEFINED ODBCABSTRACTION_REPO SET ODBCABSTRACTION_REPO="../flightsql-odbc"
 SET ODBCABSTRACTION_GIT_TAG="ed4abf01e11bca6856b15fb18312800a68372730"
+SET VCPKG_ROOT="D:/a/gh/vcpkg"
 
 cmake ..^
     -DARROW_GIT_REPOSITORY=%ARROW_GIT_REPOSITORY%^