BUG#12561297:LIBMYSQLD/EXAMPLE/MYSQL_EMBEDDED IS ABORTING.

Issue:
------
New test case mysql_embedded.test was failing on pb2.

Description:
------------
To run this test case executable libmysqld/examples/mysql_embedded is required.
But as per /libmysqld/examples/cmake_install.cmake this executable doesn't get
copied to <install_dir> when mysql is installed at <install_dir>.That is the
reason it was passing in my local branch and failed on pb2 when pushed.

Solution;
---------
Added code in mysql-test-run.pl, which will try to see if this file exists.If
It doesn't exist, test case will be skipped with a skip message. New code in
mysql-test-run.pl looks only for directory libmysqld/examples/mysql_embedded
because this is the only place where this file could/does exist.

mysql-test/mysql-test-run.pl:
  Added new variable for mysql_embedded executable.
mysql-test/t/disabled.def:
  enabled mysql_embedded.test which was disabled earlier.
mysql-test/t/mysql_embedded.test:
  Modified test case to first verify if mysql_embedded executable exists. If
  it does not, skip the test.

mysql-test/mysql-test-run.pl

@@ -171,6 +171,7 @@ our $exe_mysql;
 our $exe_mysqladmin;
 our $exe_mysqltest;
 our $exe_libtool;
+our $exe_mysql_embedded;
 
 our $opt_big_test= 0;
 
@@ -1950,6 +1951,8 @@ sub executable_setup () {
   $exe_mysqladmin=     mtr_exe_exists("$path_client_bindir/mysqladmin");
   $exe_mysql=          mtr_exe_exists("$path_client_bindir/mysql");
 
+  $exe_mysql_embedded= mtr_exe_maybe_exists("$basedir/libmysqld/examples/mysql_embedded");
+
   if ( ! $opt_skip_ndbcluster )
   {
     # Look for single threaded NDB
@@ -2354,6 +2357,7 @@ sub environment_setup {
   $ENV{'MYSQLADMIN'}=               native_path($exe_mysqladmin);
   $ENV{'MYSQL_CLIENT_TEST'}=        mysql_client_test_arguments();
   $ENV{'EXE_MYSQL'}=                $exe_mysql;
+  $ENV{'MYSQL_EMBEDDED'}=           $exe_mysql_embedded;
 
   # ----------------------------------------------------
   # bug25714 executable may _not_ exist in

mysql-test/t/disabled.def

@@ -16,4 +16,3 @@ alter_table-big          : Bug#11748731 2010-11-15 mattiasj was not tested
 create-big               : Bug#11748731 2010-11-15 mattiasj was not tested
 archive-big              : Bug#11817185 2011-03-10 Anitha Disabled since this leads to timeout on Solaris Sparc
 log_tables-big           : Bug#11756699 2010-11-15 mattiasj report already exists
-mysql_embedded           : Bug#12561297 2011-06-15 New test failing on all platforms

mysql-test/t/mysql_embedded.test

@@ -3,4 +3,10 @@
 --echo #
 
 --source include/is_embedded.inc
---exec $MYSQL_TEST_DIR/../libmysqld/examples/mysql_embedded -e 'select 1'
+
+# Test case require mysql_embedded to be present
+if(!$MYSQL_EMBEDDED)
+{
+  --skip Test requires mysql_embedded executable
+}
+--exec $MYSQL_EMBEDDED -e 'select 1'