IBMClang: Do not use -fvisibility on AIX

Use of `-fvisibility=hidden` fails:

  unsupported option '-fvisibility=hidden' for target 'powerpc-ibm-aix7.2.0.0'

Apply the change from commit 4feba34d02 (GNU: Do not use -fvisibility on
AIX or HP-UX, 2016-09-03, v3.7.0-rc1~173^2~2) to IBMClang also.

Issue: #23157

Modules/Platform/AIX-IBMClang-CXX.cmake

@@ -1,2 +1,3 @@
 include(Platform/AIX-IBMClang)
 __aix_compiler_ibmclang(CXX)
+unset(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN)

Modules/Platform/AIX-IBMClang.cmake

@@ -12,4 +12,5 @@ include(Platform/AIX-GNU)
 
 macro(__aix_compiler_ibmclang lang)
   __aix_compiler_gnu(${lang})
+  unset(CMAKE_${lang}_COMPILE_OPTIONS_VISIBILITY)
 endmacro()