Make the "system" command become executed in a bash shell in cygwin.

client/mysqltest.c:
  Prepend the command to execute by system with "sh" to make it executed by cygwin's bash
mysql-test/t/mysqldump.test:
  Change from " to ' to avoid bash's filename expanding. I.e to avoid that "[mysqltest1]" will be llok for any dirs in mysql-test/* that are named m, y, s, q etc. And ther is actually one dir called t, so we will get a match and thus echo "t" to the file.

client/mysqltest.c

@@ -1367,7 +1367,9 @@ int do_modify_var(struct st_query *query, const char *name,
 
   NOTE
    If mysqltest is executed from cygwin shell, the command will be
-   executed in cygwin shell. Thus commands like "rm" etc can be used.
+   executed in the "windows command interpreter" cmd.exe and we prepend "sh"
+   to make it be executed by cygwins "bash". Thus commands like "rm",
+   "mkdir" as well as shellscripts can executed by "system" in Windows.
  */
 
 int do_system(struct st_query *command)
@@ -1379,9 +1381,18 @@ int do_system(struct st_query *command)
 
   init_dynamic_string(&ds_cmd, 0, strlen(command->first_argument) + 64, 256);
 
+#ifdef __WIN__
+  /* Execute the command in "bash", ie. sh -c "<command>" */
+  dynstr_append(&ds_cmd, "sh -c \"");
+#endif
+
   /* Eval the system command, thus replacing all environment variables */
   do_eval(&ds_cmd, command->first_argument, TRUE);
 
+#ifdef __WIN__
+  dynstr_append(&ds_cmd, "\"");
+#endif
+
   DBUG_PRINT("info", ("running system command '%s' as '%s'",
                       command->first_argument, ds_cmd.str));
   if (system(ds_cmd.str))

mysql-test/t/mysqldump.test

@@ -830,8 +830,8 @@ DROP TABLE t1, t2;
 # Bugs #9136, #12917: problems with --defaults-extra-file option
 #
 
---system echo "[mysqltest1]" > $MYSQLTEST_VARDIR/tmp/tmp.cnf
---system echo "port=1234" >> $MYSQLTEST_VARDIR/tmp/tmp.cnf
+--system echo '[mysqltest1]' > $MYSQLTEST_VARDIR/tmp/tmp.cnf
+--system echo 'port=1234' >> $MYSQLTEST_VARDIR/tmp/tmp.cnf
 --exec $MYSQL_MY_PRINT_DEFAULTS -c $MYSQLTEST_VARDIR/tmp/tmp.cnf mysqltest1
 --exec $MYSQL_MY_PRINT_DEFAULTS -e $MYSQLTEST_VARDIR/tmp/tmp.cnf mysqltest1 mysqltest1
 --system rm $MYSQLTEST_VARDIR/tmp/tmp.cnf