RFR(S) 8021296 : [TESTBUG] Test8017498.sh fails to find "gcc" and fails to compile on some Linux releases

[Calvin Cheung]

Please review this small fix for a testcase bug.

webrev: http://cr.openjdk.java.net/~ccheung/8021296/webrev/

JBS: https://jbs.oracle.com/bugs/browse/JDK-8021296
bug: http://bugs.sun.com/view_bug.do?bug_id=8021296

Fixing 2 issues:
1) gcc not found on the test machine
     In the sh script, check for if gcc exists. If it doesn't exist, 
declare the test as "Passed".
2) REG_RIP undeclared
     REG_RIP is only defined for 64-bit linux. The compile failure was 
seen on 32-bit platform.
     The fix is to check for 64-bit platform - use REG_RIP for 64-bit 
and REG_EFL for 32-bit.
     They both have a value of 16.

Testing:
     Ran jtreg on the testcases and making sure it reports "Passed" if 
gcc isn't found.

thanks,
Calvin