CMake build infrastructure II (#53)

* CMake build infrastructure

The squashed commit that builds and packages releases for the SIMH
simulator suite with CMake, version 3.14 or newer.

See README-CMake.md for documentation.

cmake/FindPCAP.cmake

@@ -0,0 +1,76 @@
+# Locate the PCAP library
+#
+# This module defines:
+#
+# ::
+#
+#   PCAP_LIBRARIES, the name of the library to link against
+#   PCAP_INCLUDE_DIRS, where to find the headers
+#   PCAP_FOUND, if false, do not try to link against
+#   PCAP_VERSION_STRING - human-readable string containing the version of SDL_ttf
+#
+# Tweaks:
+# 1. PCAP_PATH: A list of directories in which to search
+# 2. PCAP_DIR: An environment variable to the directory where you've unpacked or installed PCAP.
+#
+# "scooter me fecit"
+
+find_path(PCAP_INCLUDE_DIR 
+    NAMES
+        pcap.h
+    HINTS
+        ENV PCAP_DIR
+    PATHS
+        pcap
+        PCAP
+        ${PCAP_PATH}
+    )
+
+# if (CMAKE_SIZEOF_VOID_P EQUAL 8)
+#     set(LIB_PATH_SUFFIXES lib64 x64 amd64 x86_64-linux-gnu aarch64-linux-gnu lib)
+# else ()
+#     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 (WIN32 AND PCAP_LIBRARY)
+#     ## Only worry about the packet library on Windows.
+#     find_library(PACKET_LIBRARY
+#         NAMES
+#             packet Packet
+#         HINTS
+#             ENV PCAP_DIR
+#         PATH_SUFFIXES
+#             ${LIB_PATH_SUFFIXES}
+#         PATHS
+#             ${PCAP_PATH}
+#     )
+# else (WIN32 AND PCAP_LIBRARY)
+#     set(PACKET_LIBRARY)
+# endif (WIN32 AND PCAP_LIBRARY)
+# ## message(STATUS "PACKET_LIBRARY is ${PACKET_LIBRARY}")
+
+# set(PCAP_LIBRARIES ${PCAP_LIBRARY} ${PACKET_LIBRARY})
+set(PCAP_INCLUDE_DIRS ${PCAP_INCLUDE_DIR})
+unset(PCAP_LIBRARY)
+unset(PCAP_INCLUDE_DIR)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(
+    PCAP
+    REQUIRED_VARS
+        ## PCAP_LIBRARIES
+        PCAP_INCLUDE_DIRS
+)