LibUSB: Improve library detection

Our FindLibUSB.cmake was previously entirely unused unless SDL was being built from Externals, we now rely on it again. It will use PkgConfig if applicable or fall back to looking around on the system, and more importantly it will always create an imported target.

CMake/FindLibUSB.cmake

@@ -11,8 +11,15 @@
 if(ANDROID)
   set(LIBUSB_FOUND FALSE CACHE INTERNAL "libusb-1.0 found")
   message(STATUS "libusb-1.0 not found.")
-elseif (NOT LIBUSB_FOUND)
-  pkg_check_modules (LIBUSB_PKG libusb-1.0)
+  return()
+endif()
+
+if(TARGET LibUSB::LibUSB)
+  return()
+endif()
+
+if(NOT LIBUSB_FOUND)
+  pkg_check_modules(LIBUSB_PKG libusb-1.0)
 
   find_path(LIBUSB_INCLUDE_DIR NAMES libusb.h
     PATHS
@@ -30,21 +37,19 @@ elseif (NOT LIBUSB_FOUND)
     /usr/local/lib
   )
 
-  if(LIBUSB_INCLUDE_DIR AND LIBUSB_LIBRARIES)
-    set(LIBUSB_FOUND TRUE CACHE INTERNAL "libusb-1.0 found")
-    message(STATUS "Found libusb-1.0: ${LIBUSB_INCLUDE_DIR}, ${LIBUSB_LIBRARIES}")
-  else(LIBUSB_INCLUDE_DIR AND LIBUSB_LIBRARIES)
-    set(LIBUSB_FOUND FALSE CACHE INTERNAL "libusb-1.0 found")
-    message(STATUS "libusb-1.0 not found.")
-  endif(LIBUSB_INCLUDE_DIR AND LIBUSB_LIBRARIES)
-
   mark_as_advanced(LIBUSB_INCLUDE_DIR LIBUSB_LIBRARIES)
-endif ()
-if(LIBUSB_FOUND AND NOT TARGET LibUSB::LibUSB)
+endif()
+
+
+if(LIBUSB_INCLUDE_DIR AND LIBUSB_LIBRARIES)
   add_library(LibUSB::LibUSB UNKNOWN IMPORTED)
   set_target_properties(LibUSB::LibUSB PROPERTIES
     IMPORTED_LOCATION "${LIBUSB_LIBRARIES}"
     INTERFACE_INCLUDE_DIRECTORIES "${LIBUSB_INCLUDE_DIR}"
   )
+  set(LIBUSB_FOUND TRUE CACHE INTERNAL "libusb-1.0 found")
+  message(STATUS "Found libusb-1.0: ${LIBUSB_INCLUDE_DIR}, ${LIBUSB_LIBRARIES}")
+else()
+  set(LIBUSB_FOUND FALSE CACHE INTERNAL "libusb-1.0 found")
+  message(STATUS "libusb-1.0 not found.")
 endif()
-

CMakeLists.txt

@@ -708,9 +708,7 @@ if(ENABLE_CUBEB)
 endif()
 
 if(NOT ANDROID)
-  dolphin_find_optional_system_library_pkgconfig(
-    LibUSB libusb-1.0 LibUSB::LibUSB Externals/libusb
-  )
+  dolphin_find_optional_system_library(LibUSB Externals/libusb)
   add_definitions(-D__LIBUSB__)
 endif()