build: remove dead code

Remove the supporting code for WITH_PTHREAD_WORKQUEUES which was removed
previously.  NFC.
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index bbc7f46..716ddd4 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -109,11 +109,6 @@
                              ${CMAKE_SOURCE_DIR}
                              ${CMAKE_CURRENT_SOURCE_DIR}
                              ${CMAKE_SOURCE_DIR}/private)
-if(WITH_PTHREAD_WORKQUEUES)
-  target_include_directories(dispatch
-                             SYSTEM BEFORE PRIVATE
-                               "${WITH_PTHREAD_WORKQUEUES}/include")
-endif()
 if(WITH_BLOCKS_RUNTIME)
   target_include_directories(dispatch
                              SYSTEM BEFORE PRIVATE
@@ -164,9 +159,6 @@
   target_link_libraries(dispatch PRIVATE ${BSD_OVERLAY_LDFLAGS})
 endif()
 target_link_libraries(dispatch PRIVATE Threads::Threads)
-if(WITH_PTHREAD_WORKQUEUES)
-  target_link_libraries(dispatch PRIVATE PTHREAD::workqueue)
-endif()
 if(WITH_BLOCKS_RUNTIME)
   target_link_libraries(dispatch PRIVATE BlocksRuntime)
 endif()
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3d5b1c1..37ab002 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -60,11 +60,6 @@
                                SYSTEM BEFORE PRIVATE
                                  "${WITH_BLOCKS_RUNTIME}")
   endif()
-  if(WITH_PTHREAD_WORKQUEUES)
-    target_include_directories(${name}
-                               SYSTEM BEFORE PRIVATE
-                                 "${WITH_PTHREAD_WORKQUEUES}/include")
-  endif()
   if(BSD_OVERLAY_FOUND)
     target_compile_options(${name}
                            PRIVATE
@@ -74,9 +69,6 @@
   # TODO(compnerd) make this portable
   target_compile_options(${name} PRIVATE -Wall -Wno-deprecated-declarations)
   target_link_libraries(${name} PRIVATE dispatch Threads::Threads)
-  if(WITH_PTHREAD_WORKQUEUES)
-    target_link_libraries(${name} PRIVATE PTHREAD::workqueue)
-  endif()
   if(WITH_BLOCKS_RUNTIME)
     target_link_libraries(${name} PRIVATE BlocksRuntime)
   endif()