RFR: 8296821: compiler/jvmci/jdk.vm.ci.code.test/src/jdk/vm/ci/code/test/NativeCallTest.java fails after JDK-8262901

[Olga Mikhaltsova]

This is a fix for a bug in the test that was added by [JDK-8262901](https://bugs.openjdk.org/browse/JDK-8262901).
The root cause of the issue was because the test returns 'int' while 'float' was expected. 

In addition the stack growth considering 16 bytes alignment in AMD64TestAssembler is fixed (similar to AArch64TestAssembler).

Tested on macOS x64 / AArch64, Linux x64 / AArch64 as follow:
` $JTREG_HOME/bin/jtreg -ea -jdk:$BUILD_HOME -nativepath:$NATIVE_PATH ./test/hotspot/jtreg/compiler/jvmci/`

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Commit messages:
 - 8296821: compiler/jvmci/jdk.vm.ci.code.test/src/jdk/vm/ci/code/test/NativeCallTest.java fails after JDK-8262901

Changes: https://git.openjdk.org/jdk/pull/11114/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11114&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296821
  Stats: 12 lines in 3 files changed: 6 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11114.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11114/head:pull/11114

PR: https://git.openjdk.org/jdk/pull/11114