[compiler-rt] Set the default C++ library to libc++ on OpenBSD (#107694)

Author: brad0

compiler-rt/CMakeLists.txt

@@ -221,7 +221,7 @@ macro(handle_default_cxx_lib var)
     set(${var}_LIBNAME "${CMAKE_MATCH_1}")
     set(${var}_SYSTEM 1)
   elseif (${var} STREQUAL "default")
-    if (APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+    if (APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD" OR CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
       set(${var}_LIBNAME "libc++")
       set(${var}_SYSTEM 1)
     elseif (FUCHSIA)