CMake: Properly include lzma include directories

CMake/DolphinLibraryTools.cmake

@@ -8,3 +8,13 @@ function(dolphin_alias_library new old)
   endif()
   add_library(${new} ALIAS _alias_${library_no_namespace})
 endfunction()
+
+# Makes an imported target if it doesn't exist.  Useful for when find scripts from older versions of cmake don't make the targets you need
+function(dolphin_make_imported_target_if_missing target lib)
+  if(${lib}_FOUND AND NOT TARGET ${target})
+    add_library(_${lib} INTERFACE)
+    target_link_libraries(_${lib} INTERFACE "${${lib}_LIBRARIES}")
+    target_include_directories(_${lib} INTERFACE "${${lib}_INCLUDE_DIRS}")
+    add_library(${target} ALIAS _${lib})
+  endif()
+endfunction()

CMakeLists.txt

@@ -761,16 +761,13 @@ endif()
 
 # macOS ships with liblzma.dylib but no headers, so check for the headers too
 find_package(LibLZMA)
-check_include_file(lzma.h HAVE_LZMA_H)
-if(LIBLZMA_FOUND AND HAVE_LZMA_H)
+if(LIBLZMA_FOUND)
+  # Imported target added in CMake 3.14
+  dolphin_make_imported_target_if_missing(LibLZMA::LibLZMA LIBLZMA)
   message(STATUS "Using shared lzma")
 else()
   check_vendoring_approved(lzma)
-  if(LIBLZMA_FOUND AND NOT HAVE_LZMA_H)
-    message(STATUS "Shared lzma found but lacks headers, falling back to the static library")
-  else()
   message(STATUS "Shared lzma not found, falling back to the static library")
-  endif()
   add_subdirectory(Externals/liblzma)
 endif()
 

Source/Core/DiscIO/CMakeLists.txt

@@ -70,7 +70,7 @@ target_link_libraries(discio
 PUBLIC
   core
   BZip2::BZip2
-  lzma
+  LibLZMA::LibLZMA
   zstd::zstd
 
 PRIVATE