RFR: JDK-8190418 Stop generating jvmtiEnvStub and jvmtiEnvRecommended

[Magnus Ihse Bursie]

During hotspot gensrc, we create two files, jvmtiEnvStub and 
jvmtiEnvRecommended, which later on are explicitly excluded from the 
build. We should just stop generating them.

I have built hotspot with and without this patch, and used the build 
comparison script (compare.sh) to verify that it has not changed.

Bug: https://bugs.openjdk.java.net/browse/JDK-8190418
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8190418-stop-generating-unneeded-jvmti-files/webrev.01

/Magnus