[CMake] Use a custom variable for libdir path

CMAKE_INSTALL_LIBDIR has wrong value during a clean build for some
reason.

Author: aciidgh

CMakeLists.txt

@@ -22,7 +22,7 @@ include(CheckLibraryExists)
 include(CheckSymbolExists)
 include(GNUInstallDirs)
 
-set(CMAKE_INSTALL_LIBDIR lib CACHE PATH "Path where the libraries should be installed")
+set(INSTALL_LIBDIR "lib" CACHE PATH "Path where the libraries should be installed")
 set(WITH_BLOCKS_RUNTIME "" CACHE PATH "Path to blocks runtime")
 
 include(DispatchAppleOptions)

dispatch/CMakeLists.txt

@@ -14,12 +14,12 @@ install(FILES
           source.h
           time.h
         DESTINATION
-          "${CMAKE_INSTALL_LIBDIR}/swift/dispatch")
+          "${INSTALL_LIBDIR}/swift/dispatch")
 if(ENABLE_SWIFT)
   get_filename_component(MODULE_MAP module.modulemap REALPATH)
   install(FILES
             ${MODULE_MAP}
           DESTINATION
-            "${CMAKE_INSTALL_LIBDIR}/swift/dispatch")
+            "${INSTALL_LIBDIR}/swift/dispatch")
 endif()
 

os/CMakeLists.txt

@@ -6,5 +6,5 @@ install(FILES
           object.h
           linux_base.h
         DESTINATION
-          "${CMAKE_INSTALL_LIBDIR}/swift/os")
+          "${INSTALL_LIBDIR}/swift/os")
 

src/CMakeLists.txt

@@ -202,12 +202,12 @@ add_custom_command(TARGET dispatch POST_BUILD
 install(TARGETS
           dispatch
         DESTINATION
-          "${CMAKE_INSTALL_LIBDIR}/swift/${SWIFT_OS}")
+          "${INSTALL_LIBDIR}/swift/${SWIFT_OS}")
 if(ENABLE_SWIFT)
   install(FILES
             ${CMAKE_CURRENT_BINARY_DIR}/swift/Dispatch.swiftmodule
             ${CMAKE_CURRENT_BINARY_DIR}/swift/Dispatch.swiftdoc
           DESTINATION
-            "${CMAKE_INSTALL_LIBDIR}/swift/${SWIFT_OS}/${CMAKE_SYSTEM_PROCESSOR}")
+            "${INSTALL_LIBDIR}/swift/${SWIFT_OS}/${CMAKE_SYSTEM_PROCESSOR}")
 endif()