Fix test that did not work in out-of-source build .

There are 2 different share directories, one if builddir/share (with compiled errmsg.sys) 
and another one is $sourcedir/share and contains some /charsets/*.xml files.
second one should be refered to  as MYSQL_CHARSETSDIR and  MYSQL_SHAREDIR  $builddir/share

mysql-test/suite/sys_vars/r/character_sets_dir_basic.result

 select @@global.character_sets_dir;
 @@global.character_sets_dir
-MYSQL_SHAREDIR/charsets/
+MYSQL_CHARSETSDIR/
 select @@session.character_sets_dir;
 ERROR HY000: Variable 'character_sets_dir' is a GLOBAL variable
 show global variables like 'character_sets_dir';
 Variable_name	Value
-character_sets_dir	MYSQL_SHAREDIR/charsets/
+character_sets_dir	MYSQL_CHARSETSDIR/
 show session variables like 'character_sets_dir';
 Variable_name	Value
-character_sets_dir	MYSQL_SHAREDIR/charsets/
+character_sets_dir	MYSQL_CHARSETSDIR/
 select * from information_schema.global_variables where variable_name='character_sets_dir';
 VARIABLE_NAME	VARIABLE_VALUE
-CHARACTER_SETS_DIR	MYSQL_SHAREDIR/charsets/
+CHARACTER_SETS_DIR	MYSQL_CHARSETSDIR/
 select * from information_schema.session_variables where variable_name='character_sets_dir';
 VARIABLE_NAME	VARIABLE_VALUE
-CHARACTER_SETS_DIR	MYSQL_SHAREDIR/charsets/
+CHARACTER_SETS_DIR	MYSQL_CHARSETSDIR/
 set global character_sets_dir="foo";
 ERROR HY000: Variable 'character_sets_dir' is a read only variable
 set session character_sets_dir="foo";

mysql-test/suite/sys_vars/t/character_sets_dir_basic.test

 #
 # show the global and session values;
 #
---replace_result $MYSQL_SHAREDIR MYSQL_SHAREDIR
+--replace_result $MYSQL_CHARSETSDIR MYSQL_CHARSETSDIR
 select @@global.character_sets_dir;
 --error ER_INCORRECT_GLOBAL_LOCAL_VAR
 select @@session.character_sets_dir;
---replace_result $MYSQL_SHAREDIR MYSQL_SHAREDIR
+--replace_result $MYSQL_CHARSETSDIR MYSQL_CHARSETSDIR
 show global variables like 'character_sets_dir';
---replace_result $MYSQL_SHAREDIR MYSQL_SHAREDIR
+--replace_result $MYSQL_CHARSETSDIR MYSQL_CHARSETSDIR
 show session variables like 'character_sets_dir';
---replace_result $MYSQL_SHAREDIR MYSQL_SHAREDIR
+--replace_result $MYSQL_CHARSETSDIR MYSQL_CHARSETSDIR
 select * from information_schema.global_variables where variable_name='character_sets_dir';
---replace_result $MYSQL_SHAREDIR MYSQL_SHAREDIR
+--replace_result $MYSQL_CHARSETSDIR MYSQL_CHARSETSDIR
 select * from information_schema.session_variables where variable_name='character_sets_dir';
 
 #