[libcxxabi][cmake] Account for LIBCXXABI_TARGET_SUBDIR in test config

This makes the logic and code structure match that of libc++, which handles this case.
The `%{target}` substitution from libc++ is removed as libc++abi's config seems to be the only place it's used.

Author: tambry

libcxx/utils/libcxx/test/params.py

@@ -170,7 +170,6 @@ def getSuitableClangTidy(cfg):
             [
                 AddFeature("target={}".format(triple)),
                 AddFlagIfSupported("--target={}".format(triple)),
-                AddSubstitution("%{triple}", triple),
             ],
         ),
     ),

libcxxabi/CMakeLists.txt

@@ -191,6 +191,8 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(LIBCXXABI_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LIBCXXABI_TARGET_SUBDIR})
   set(LIBCXXABI_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LIBCXXABI_TARGET_SUBDIR} CACHE STRING
       "Path where built libc++abi libraries should be installed.")
+  set(LIBCXXABI_INSTALL_INCLUDE_TARGET_DIR "${CMAKE_INSTALL_INCLUDEDIR}/${LIBCXXABI_TARGET_SUBDIR}/c++/v1" CACHE STRING
+      "Path where target-specific libc++abi headers should be installed.")
   unset(LIBCXXABI_TARGET_SUBDIR)
 else()
   if(LLVM_LIBRARY_OUTPUT_INTDIR)
@@ -202,6 +204,8 @@ else()
   endif()
   set(LIBCXXABI_INSTALL_LIBRARY_DIR lib${LIBCXXABI_LIBDIR_SUFFIX} CACHE STRING
       "Path where built libc++abi libraries should be installed.")
+  set(LIBCXXABI_INSTALL_INCLUDE_TARGET_DIR "${LIBCXXABI_INSTALL_INCLUDE_DIR}" CACHE STRING
+      "Path where target-specific libc++abi headers should be installed.")
 endif()
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LIBCXXABI_LIBRARY_DIR})

libcxxabi/test/configs/cmake-bridge.cfg.in

@@ -30,7 +30,7 @@ config.substitutions.append(('%{libcxx}', '@LIBCXXABI_LIBCXX_PATH@'))
 config.substitutions.append(('%{install-prefix}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@'))
 config.substitutions.append(('%{include}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@/include'))
 config.substitutions.append(('%{cxx-include}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@/@LIBCXXABI_INSTALL_INCLUDE_DIR@'))
-config.substitutions.append(('%{cxx-target-include}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@/include/%{triple}/c++/v1'))
+config.substitutions.append(('%{cxx-target-include}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@/@LIBCXXABI_INSTALL_INCLUDE_TARGET_DIR@'))
 config.substitutions.append(('%{lib}', '@LIBCXXABI_TESTING_INSTALL_PREFIX@/@LIBCXXABI_INSTALL_LIBRARY_DIR@'))
 config.substitutions.append(('%{benchmark_flags}', ''))