As of 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 was removed by JDK-8327701.
Now we also switch the HOTSPOT_TOOLCHAIN_TYPE from xlc to gcc, removing the last xlc rudiment.
This means merging the AIX specific content of utilities/globalDefinitions_xlc.hpp and utilities/compilerWarnings_xlc.hpp into the corresponding gcc files on the on side and removing the defined(TARGET_COMPILER_xlc) blocks in the code, because the defined(TARGET_COMPILER_gcc) blocks work out of the box for the new AIX compiler.
The rest of the changes are needed because of using utilities/compilerWarnings_xlc.hpp the compiler is much more nagging about ill formatted printf