RFR(S): 8203354: assert in ClassLoader::update_module_path_entry_list() could have incorrect message

[Calvin Cheung]

JBS: https://bugs.openjdk.java.net/browse/JDK-8203354

webrev: http://cr.openjdk.java.net/~ccheung/8203354/webrev.00/

Converting the assert in ClassLoader::update_module_path_entry_list() to 
a meaningful error message before aborting the CDS dump.

With a module path with very long length (> 2K), the error message will 
be like the following:

os::stat error 36 (ENAMETOOLONG). CDS dump aborted. Bad path 
/scratch/myDir/JTwork/scratch/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx <snip>

Note that tty->print_cr() has a buffer size limit of 2000, so the full 
path won't be shown entirely. That's why I'd like to put the error code 
up front before the path.

Ran the modified tests on Oracle platforms.

thanks,
Calvin