Reapply [libomptarget] Build plugins-nextgen for SystemZ (#83978)

The plugin was not getting built as the build_generic_elf64 macro
assumes the LLVM triple processor name matches the CMake processor name,
which is unfortunately not the case for SystemZ.

Fix this by providing two separate arguments instead.

Actually building the plugin exposed a number of other issues causing
various test failures. Specifically, I've had to add the SystemZ target
to
- CompilerInvocation::ParseLangArgs
- linkDevice in ClangLinuxWrapper.cpp
- OMPContext::OMPContext (to set the device_kind_cpu trait)
- LIBOMPTARGET_ALL_TARGETS in libomptarget/CMakeLists.txt
- a check_plugin_target call in libomptarget/src/CMakeLists.txt

Finally, I've had to set a number of test cases to UNSUPPORTED on
s390x-ibm-linux-gnu; all these tests were already marked as UNSUPPORTED
for x86_64-pc-linux-gnu and aarch64-unknown-linux-gnu and are failing on
s390x for what seem to be the same reason.

In addition, this also requires support for BE ELF files in
plugins-nextgen: https://github.com/llvm/llvm-project/pull/85246

1 files changed, 1 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 451bdb9..2d3cbb9 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4014,6 +4014,7 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
       if (TT.getArch() == llvm::Triple::UnknownArch ||
           !(TT.getArch() == llvm::Triple::aarch64 || TT.isPPC() ||
+            TT.getArch() == llvm::Triple::systemz ||
             TT.getArch() == llvm::Triple::nvptx ||
             TT.getArch() == llvm::Triple::nvptx64 ||
             TT.getArch() == llvm::Triple::amdgcn ||