Merge #74: Add install-lib and install-bin build targets

fa130db Add `install-bin` target (Hennadii Stepanov)
c4d26d2 Add `install-lib` target (Hennadii Stepanov)
bc3d166 Install `proxy.capnp` with `mpgen` target (Hennadii Stepanov)

Pull request description:

  This PR adds new `install-lib` and `install-bin` build targets which allow to build and install only required artifacts during different stages of cross-building.

  A demo, which uses this branch in Bitcoin Core, is [here](https://github.com/hebasto/bitcoin/commits/220907-mp-demo).

ACKs for top commit:
  ryanofsky:
    Code review ACK fa130db. This does exactly what I'd expect now, so will merge it. But you do bring up an important point about no longer exporting cmake targets.

Tree-SHA512: 2146913594c2ad4570ac4fb77d09297bb0ddcd0c8cd38527db0cfc04b98d099a0e6c97e7b4cbed64f78da6ba7c98bdafa20c4c9cc20db1da3d57dadee7c88899

Author: ryanofsky

CMakeLists.txt

@@ -58,7 +58,6 @@ set(MP_PUBLIC_HEADERS
   ${MP_PROXY_HDRS}
   include/mp/proxy-io.h
   include/mp/proxy-types.h
-  include/mp/proxy.capnp
   include/mp/proxy.h
   include/mp/util.h)
 
@@ -78,7 +77,15 @@ target_link_libraries(multiprocess PRIVATE CapnProto::kj)
 target_link_libraries(multiprocess PRIVATE CapnProto::kj-async)
 set_target_properties(multiprocess PROPERTIES
     PUBLIC_HEADER "${MP_PUBLIC_HEADERS}")
-install(TARGETS multiprocess EXPORT Multiprocess ARCHIVE DESTINATION lib PUBLIC_HEADER DESTINATION include/mp)
+install(TARGETS multiprocess EXPORT Multiprocess
+  ARCHIVE DESTINATION lib COMPONENT lib
+  PUBLIC_HEADER DESTINATION include/mp COMPONENT lib)
+install(FILES "${CMAKE_CURRENT_BINARY_DIR}/pkgconfig/libmultiprocess.pc"
+  DESTINATION "lib/pkgconfig" COMPONENT lib)
+add_custom_target(install-lib
+  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=lib -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
+  VERBATIM)
+add_dependencies(install-lib multiprocess)
 
 add_executable(mpgen src/mp/gen.cpp $<TARGET_OBJECTS:util>)
 target_include_directories(mpgen PRIVATE $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>)
@@ -90,12 +97,20 @@ target_link_libraries(mpgen PRIVATE CapnProto::kj)
 target_link_libraries(mpgen PRIVATE Threads::Threads)
 set_target_properties(mpgen PROPERTIES
     INSTALL_RPATH_USE_LINK_PATH TRUE)
-install(TARGETS mpgen EXPORT Multiprocess RUNTIME DESTINATION bin)
+set_target_properties(mpgen PROPERTIES
+    PUBLIC_HEADER include/mp/proxy.capnp)
+install(TARGETS mpgen EXPORT Multiprocess
+  RUNTIME DESTINATION bin COMPONENT bin
+  PUBLIC_HEADER DESTINATION include/mp COMPONENT bin)
+install(FILES "include/mpgen.mk"
+  DESTINATION "include" COMPONENT bin)
+add_custom_target(install-bin
+  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=bin -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
+  VERBATIM)
+add_dependencies(install-bin mpgen)
 
 configure_file(include/mp/config.h.in "${CMAKE_CURRENT_BINARY_DIR}/include/mp/config.h")
 configure_file(pkgconfig/libmultiprocess.pc.in "${CMAKE_CURRENT_BINARY_DIR}/pkgconfig/libmultiprocess.pc" @ONLY)
-install(FILES "${CMAKE_CURRENT_BINARY_DIR}/pkgconfig/libmultiprocess.pc" DESTINATION "lib/pkgconfig")
-install(FILES "include/mpgen.mk" DESTINATION "include")
 
 install(EXPORT Multiprocess DESTINATION lib/cmake/Multiprocess)