Update CMakeLists.txt to install the cmake bindings in the right location

/usr/lib/cpprestsdk is not the correct FHS standard cmake location.
It should be placed in /usr/lib/<triplet>/cmake/cpprestsdk instead.

Same goes for libraries, support multiarch location if we use UNIX

Author: LocutusOfBorg

Release/CMakeLists.txt

@@ -18,7 +18,6 @@ enable_testing()
 set(WERROR ON CACHE BOOL "Treat Warnings as Errors.")
 set(CPPREST_EXCLUDE_WEBSOCKETS OFF CACHE BOOL "Exclude websockets functionality.")
 set(CPPREST_EXCLUDE_COMPRESSION OFF CACHE BOOL "Exclude compression functionality.")
-set(CPPREST_EXPORT_DIR lib/cpprestsdk CACHE STRING "Directory to install CMake config files.")
 set(CPPREST_INSTALL_HEADERS ON CACHE BOOL "Install header files.")
 set(CPPREST_INSTALL ON CACHE BOOL "Add install commands.")
 
@@ -63,6 +62,9 @@ include(cmake/cpprest_find_zlib.cmake)
 include(cmake/cpprest_find_openssl.cmake)
 include(cmake/cpprest_find_websocketpp.cmake)
 include(CheckIncludeFiles)
+if(UNIX)
+include(GNUInstallDirs)
+endif(UNIX)
 
 find_package(Threads REQUIRED)
 if(THREADS_HAVE_PTHREAD_ARG)

Release/src/CMakeLists.txt

@@ -250,21 +250,21 @@ if(CPPREST_INSTALL)
   install(
     TARGETS ${CPPREST_TARGETS}
     EXPORT cpprestsdk-targets
-    RUNTIME DESTINATION bin
-    LIBRARY DESTINATION lib
-    ARCHIVE DESTINATION lib
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
   )
 
   configure_file(../cmake/cpprestsdk-config.in.cmake "${CMAKE_CURRENT_BINARY_DIR}/cpprestsdk-config.cmake" @ONLY)
 
   install(
     FILES "${CMAKE_CURRENT_BINARY_DIR}/cpprestsdk-config.cmake"
-    DESTINATION ${CPPREST_EXPORT_DIR}
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake
   )
   install(
     EXPORT cpprestsdk-targets
     FILE cpprestsdk-targets.cmake
     NAMESPACE cpprestsdk::
-    DESTINATION ${CPPREST_EXPORT_DIR}
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake
   )
 endif()