RFR: JDK-8072904: building jdk9 with jdk9 boot jdk can cause failure or incorrect results

[Erik Joelsson]

Hello,

Please review this change to how javah is run on sa classes. Since the 
sa classes in JDK 9 are now in a module instead of sa-jdi.jar, they are 
(at least currently) available from the default bootclasspath. This 
means that just setting -classpath to javah will not properly override 
the versions of the classes found in the boot jdk with the versions 
currently being built. The fix is to change -classpath with 
-Xbootclasspath/p:.

Bug: https://bugs.openjdk.java.net/browse/JDK-8072904
Webrev: http://cr.openjdk.java.net/~erikj/8072904/webrev.hotspot.01/

Planning to push this through jdk9/hs-rt.

/Erik