These are some small changes (basically platform detection and exclusion of some tests) to fix the jtreg tests on Linux/s390x.

Base repository:
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Add isS390x() to platform.java. Sort checks alphabetically.
Add s390x to shouldSAAttach.

Hotspot repository:
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compiler/ciReplay/SABase.java
SA writes "Command not valid until the attached to a VM" to test_replay.txt.
Disable test is SA not supported.

compiler/intrinsics/sha/cli/...
Add checks for corresponding cpu feature.

Adapt test_env.sh and TestMutuallyExclusivePlatformPredicates.java

jdk repostiory:
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test/java/awt/JAWT/JAWT.sh
Exclude this test.

test/sun/tools/jhsdb/heapconfig/...
Use Platform.java from base repo which known that s390 does not support SA.