wrote manpage in c3c.1 and added manpage install to CMakeLists.txt

CMakeLists.txt

@@ -525,6 +525,17 @@ endif()
 install(TARGETS c3c DESTINATION bin)
 install(DIRECTORY lib/ DESTINATION lib/c3)
 
+# Man page install (OSX/Linux only)
+set(MAN_PAGE_DIR "/usr/local/share/man/man1")
+message(STATUS "installing man page to ${MAN_PAGE_DIR}")
+
+if (NOT WIN32 AND EXISTS "${MAN_PAGE_DIR}")
+    install(FILES c3c.1 DESTINATION ${MAN_PAGE_DIR})
+elseif (NOT WIN32)
+    # won't create MAN_PAGE_DIR if it doesn't already exist
+    message(WARNING "Man page directory ${MAN_PAGE_DIR} does not exist, skipping man page installation")
+endif()
+
 if (C3_WITH_LLVM AND DEFINED sanitizer_runtime_libraries)
     add_custom_command(TARGET c3c POST_BUILD
         COMMAND "${CMAKE_COMMAND}" -E rm -rf -- $<TARGET_FILE_DIR:c3c>/c3c_rt