fix(cmake): output was not exported

Signed-off-by: Henry Schreiner <[email protected]>

tools/pybind11Common.cmake

@@ -262,19 +262,16 @@ include(CheckCXXCompilerFlag)
 # cached base on the result variable.  If the flags work, sets them in
 # cxxflags_out/linkerflags_out internal cache variables (in addition to
 # ${result}).
-function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerflags cxxflags_out
-         linkerflags_out)
+macro(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerflags cxxflags_out
+      linkerflags_out)
   set(CMAKE_REQUIRED_LIBRARIES ${linkerflags})
   check_cxx_compiler_flag("${cxxflags}" ${result})
   if(${result})
-    set(${cxxflags_out}
-        "${cxxflags}"
-        PARENT_SCOPE)
-    set(${linkerflags_out}
-        "${linkerflags}"
-        PARENT_SCOPE)
+    set(${cxxflags_out} "${cxxflags}")
+    set(${linkerflags_out} "${linkerflags}")
   endif()
-endfunction()
+  unset(CMAKE_REQUIRED_LIBRARIES)
+endmacro()
 
 function(_pybind11_generate_lto target prefer_thin_lto)
   if(MINGW)