FS-10455: [build] add small configure check to determine V8_TARGET for GN build

configure.ac

@@ -1550,6 +1550,13 @@ AC_ARG_ENABLE(parallel-build-v8,
 [AS_HELP_STRING([--disable-parallel-build-v8], [Disable parallel build of V8])], [enable_parallel_build_v8="$enableval"], [enable_parallel_build_v8="yes"])
 AM_CONDITIONAL([ENABLE_PARALLEL_BUILD_V8],[test "x$enable_parallel_build_v8" != "xno"])
 
+if test "`uname -m`" = "x86_64"; then
+	V8_TARGET="x64"
+else
+	V8_TARGET="x86"
+fi
+AC_SUBST(V8_TARGET)
+   
 AM_CONDITIONAL([HAVE_ODBC],[test "x$enable_core_odbc_support" != "xno"])
 AM_CONDITIONAL([HAVE_MYSQL],[test "$found_mysql" = "yes"])