FreeBSD: link against libpcap

On FreeBSD, one must actually link against libpcap
(or give the path to a shared object at link
time).  That is, it is not a header-only library
on that platform.

Account for this by adding a new boolean variable
in `platform-quirks.cmake`: `NEED_PCAP_LIBRARY`,
which defaults to false.  Condition pcap library
discovery and link argument modifications on that
variable in `FindPCAP.cmake` and `dep-link.cmake`.

Author: Dan Cross

cmake/FindPCAP.cmake

@@ -32,18 +32,20 @@ find_path(PCAP_INCLUDE_DIR
 #     set(LIB_PATH_SUFFIXES x86)
 # endif ()
 
-# find_library(PCAP_LIBRARY
-#         NAMES
-#             pcap pcap_static libpcap libpcap_static
-#         HINTS
-#             ENV PCAP_DIR
-#         PATH_SUFFIXES
-#             ${LIB_PATH_SUFFIXES}
-#         PATHS
-#             ${PCAP_PATH}
-#         )
-# ## message(STATUS "LIB_PATH_SUFFIXES ${LIB_PATH_SUFFIXES}")
-# ## message(STATUS "PCAP_LIBRARY is ${PCAP_LIBRARY}")
+if (NEED_PCAP_LIBRARY)
+    find_library(PCAP_LIBRARY
+            NAMES
+                pcap pcap_static libpcap libpcap_static
+            HINTS
+                ENV PCAP_DIR
+            PATH_SUFFIXES
+                ${LIB_PATH_SUFFIXES}
+            PATHS
+                ${PCAP_PATH}
+            )
+    message(STATUS "LIB_PATH_SUFFIXES ${LIB_PATH_SUFFIXES}")
+    message(STATUS "PCAP_LIBRARY is ${PCAP_LIBRARY}")
+endif()
 
 # if (WIN32 AND PCAP_LIBRARY)
 #     ## Only worry about the packet library on Windows.
@@ -62,15 +64,25 @@ find_path(PCAP_INCLUDE_DIR
 # endif (WIN32 AND PCAP_LIBRARY)
 # ## message(STATUS "PACKET_LIBRARY is ${PACKET_LIBRARY}")
 
-# set(PCAP_LIBRARIES ${PCAP_LIBRARY} ${PACKET_LIBRARY})
+if (NEED_PCAP_LIBRARY)
+    set(PCAP_LIBRARIES ${PCAP_LIBRARY} ${PACKET_LIBRARY})
+endif()
 set(PCAP_INCLUDE_DIRS ${PCAP_INCLUDE_DIR})
 unset(PCAP_LIBRARY)
 unset(PCAP_INCLUDE_DIR)
 
 include(FindPackageHandleStandardArgs)
+if (NEED_PCAP_LIBRARY)
+find_package_handle_standard_args(
+    PCAP
+    REQUIRED_VARS
+        PCAP_LIBRARIES
+        PCAP_INCLUDE_DIRS
+)
+else()
 find_package_handle_standard_args(
     PCAP
     REQUIRED_VARS
-        ## PCAP_LIBRARIES
         PCAP_INCLUDE_DIRS
 )
+endif()

cmake/dep-link.cmake

@@ -311,6 +311,10 @@ if (WITH_NETWORK)
             endforeach()
 
             target_include_directories(simh_network INTERFACE "${PCAP_INCLUDE_DIRS}")
+            if (NEED_PCAP_LIBRARY)
+                target_link_directories(simh_network INTERFACE "${PCAP_LIBRARY_DIRS}")
+                target_link_libraries(simh_network INTERFACE "${PCAP_LIBRARIES}")
+            endif ()
             target_compile_definitions(simh_network INTERFACE HAVE_PCAP_NETWORK)
         endif ()
     endif ()

cmake/platform-quirks.cmake

@@ -264,3 +264,8 @@ if (CMAKE_HOST_APPLE)
         set(CMAKE_OSX_ARCHITECTURES "arm64;x86_64")
     endif ()
 endif()
+
+set(NEED_PCAP_LIBRARY FALSE)
+if (${CMAKE_HOST_SYSTEM_NAME} MATCHES "FreeBSD")
+    set(NEED_PCAP_LIBRARY TRUE)
+endif()