c wrapper: add pkg-config file

CMakeLists.txt

@@ -322,6 +322,13 @@ if (OPENDHT_C)
     )
     target_compile_definitions(opendht-c PRIVATE OPENDHT_C_BUILD)
     target_link_libraries(opendht-c opendht)
+    # PkgConfig module
+    configure_file (
+        opendht-c.pc.in
+        opendht-c.pc
+        @ONLY
+    )
+    install (FILES ${CMAKE_CURRENT_BINARY_DIR}/opendht-c.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 endif ()
 
 if (OPENDHT_TOOLS)

opendht-c.pc.in

+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+Name: OpenDHT (C Wrapper)
+Description: Distributed Hash Table library (C Wrapper)
+Version: @VERSION@
+Libs: -L${libdir} -lopendht-c
+Requires.private: opendht gnutls >= 3.1 @argon2_lib@
+Cflags: -I${includedir}