RFR: 8327701: Remove the xlc toolchain [v2]

[Joachim Kern]

On Fri, 8 Mar 2024 15:48:08 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 one additional commit since the last revision:
> 
>   Revert SEARCH_PATH changes

make/autoconf/toolchain.m4 line 940:

> 938:   if test "x$OPENJDK_TARGET_OS" = xaix; then
> 939:     # Make sure we have the Open XL version of clang on AIX
> 940:     $ECHO "$CC_VERSION_OUTPUT" | $GREP "IBM Open XL C/C++ for AIX" > /dev/null

This does not work since $CC_VERSION_OUTPUT is unset. We need 
	CC_VERSION_OUTPUT=`${XLC_TEST_PATH}ibm-clang++_r --version 2>&1 | $HEAD -n 1`
before, as in the previous code some lines above which you removed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18172#discussion_r1519634810