$OpenBSD$

Do not link -lstdc++ when using clang.
Remove hardcoded -O2.

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -77,14 +77,14 @@ llvm_map_components_to_libnames(LLVM_COMMON_LIBS suppo
 
 if(CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang"))
    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -lstdc++")
+     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
      if(GCC)
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --gcc-toolchain=${GCC}")
      endif()
    endif()
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic")
-   set(CMAKE_CXX_FLAGS_RELEASE    "-O2 -DDEBUG")
+   set(CMAKE_CXX_FLAGS_RELEASE    "-DDEBUG")
    set(CMAKE_CXX_FLAGS_MINSIZEREL "-O2 '-DCHECK=(void)'")
    set(CMAKE_CXX_FLAGS_DEBUG      "-g -DDEBUG")
 
