RFR: 8327701: Remove the xlc toolchain [v4]

[Joachim Kern]

On Tue, 12 Mar 2024 15:27:29 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> As of [JDK-8325880](https://bugs.openjdk.org/browse/JDK-8325880), building the JDK requires version 17 of IBM Open XL C/C++ (xlc). This is in effect clang by another name, and it uses the clang toolchain in the JDK build. Thus the old xlc toolchain is no longer supported, and should be removed.
>
> Magnus Ihse Bursie has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Replace CC_VERSION_OUTPUT with CC_VERSION_STRING
>  - We need CC_VERSION_OUTPUT before we can check it

e.g. We should change the HOTSPOT_TOOLCHAIN_TYPE=xlc to aix, because it is not toolchain, but OS related. As a consequence the globalDefinitions_xlc.hpp will become globalDefinitions_aix.hpp

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PR Comment: https://git.openjdk.org/jdk/pull/18172#issuecomment-1993979991