[clang][tests] Fix ve-toolchain tests with CLANG_DEFAULT_UNWINDLIB

[tbaeder]

Summary

Otherwise, the

// DEF-SAME: "[[RESOURCE_DIR]]/lib/linux/libclang_rt.builtins-ve.a" "-lc"

line ends up getting a -lgcc_s inserted in between and the output doesn't match anymore.
Also fix a -stdlib=c++ now that I'm already looking at it.

[tbaeder]

The failing tests seem all omp related and not about this change.

[simoll]

LGTM. For the record, this is related to the issues with the -fuse-ld option in that a cmake flag globally overrides a toolchain default: https://reviews.llvm.org/D115045.

clang/test/Driver/ve-toolchain.c

 ///  - dynamic linker
 ///  - library paths
 ///  - nld VE specific options
 ///  - sjlj exception
 
 // RUN: %clang -### -target ve-unknown-linux-gnu \
 // RUN:     --sysroot %S/Inputs/basic_ve_tree \
 // RUN:     -resource-dir=%S/Inputs/basic_ve_tree/resource_dir \
+// RUN:     --unwindlib=none \
 // RUN:     -fuse-ld=ld \
 // RUN:     %s 2>&1 | FileCheck -check-prefix=DEF %s
 
 // DEF:      clang{{.*}}" "-cc1"
 // DEF-SAME: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // DEF-SAME: "-isysroot" "[[SYSROOT:[^"]+]]"
 // DEF-SAME: "-exception-model=sjlj"
 // DEF:      nld"

clang/test/Driver/ve-toolchain.cpp

 ///  - library paths
 ///  - nld VE specific options
 ///  - sjlj exception
 
 // RUN: %clangxx -### -target ve-unknown-linux-gnu \
 // RUN:     --sysroot %S/Inputs/basic_ve_tree \
 // RUN:     -fuse-ld=ld \
 // RUN:     -resource-dir=%S/Inputs/basic_ve_tree/resource_dir \
-// RUN:     --stdlib=c++ %s 2>&1 | FileCheck -check-prefix=DEF %s
+// RUN:     --unwindlib=none \
+// RUN:     --stdlib=libc++ %s 2>&1 | FileCheck -check-prefix=DEF %s
 
 // DEF:      clang{{.*}}" "-cc1"
 // DEF-SAME: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // DEF-SAME: "-isysroot" "[[SYSROOT:[^"]+]]"
 // DEF-SAME: "-exception-model=sjlj"
 // DEF:      nld"
 // DEF-SAME: "--sysroot=[[SYSROOT]]"
 // DEF-SAME: "-dynamic-linker" "/opt/nec/ve/lib/ld-linux-ve.so.1"