cmake: Use autotools to build libusb generally for GNU

Building libusb was also broken on GCC (and maybe Clang) on our
CMakeLists after upgrading to 1.0.24, but it was not being checked
because our 18.04 container had libusb installed on it.
This builds on the MinGW work from earlier and extends it to the rest of
the GNU toolchains. In addition we make use of pkg-config when present
to find libusb. pkg-config is preferrable because we can specify a
minimum required version.

1 files changed, 28 insertions, 16 deletions

diff --git a/externals/libusb/CMakeLists.txt b/externals/libusb/CMakeLists.txt
index 3ef007b40..da6d68684 100644
--- a/externals/libusb/CMakeLists.txt
+++ b/externals/libusb/CMakeLists.txt
@@ -1,10 +1,10 @@
-if (MINGW)
-    # The MinGW toolchain for some reason doesn't work with this CMakeLists file after updating to
-    # 1.0.24, so we do it the old-fashioned way for now. We may want to move native Linux toolchains
-    # to here, too (TODO lat9nq?).
+if (MINGW OR NOT WIN32)
+    # GNU toolchains for some reason doesn't work with the later half of this CMakeLists after
+    # updating to 1.0.24, so we do it the old-fashioned way for now.
 
     set(LIBUSB_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/libusb")
     set(LIBUSB_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/libusb")
+
     # Workarounds for MSYS/MinGW
     if (MSYS)
         # CMake on Windows passes `C:/`, but we need `/C/` or `/c/` to use `configure`
@@ -19,9 +19,18 @@ if (MINGW)
 
     set(LIBUSB_CONFIGURE "${LIBUSB_SRC_DIR}/configure")
     set(LIBUSB_MAKEFILE "${LIBUSB_PREFIX}/Makefile")
-    set(LIBUSB_LIBRARY "${LIBUSB_PREFIX}/libusb/.libs/libusb-1.0.dll.a")
-    set(LIBUSB_SHARED_LIBRARY "${LIBUSB_PREFIX}/libusb/.libs/libusb-1.0.dll")
-    set(LIBUSB_SHARED_LIBRARY_DEST "${CMAKE_BINARY_DIR}/bin/libusb-1.0.dll")
+
+    if (MINGW)
+        set(LIBUSB_LIBRARY "${LIBUSB_PREFIX}/libusb/.libs/libusb-1.0.dll.a")
+        set(LIBUSB_SHARED_LIBRARY "${LIBUSB_PREFIX}/libusb/.libs/libusb-1.0.dll")
+        set(LIBUSB_SHARED_LIBRARY_DEST "${CMAKE_BINARY_DIR}/bin/libusb-1.0.dll")
+
+        set(LIBUSB_CONFIGURE_ARGS --host=x86_64-w64-mingw32 --build=x86_64-windows)
+    else()
+        set(LIBUSB_LIBRARY "${LIBUSB_PREFIX}/libusb/.libs/libusb-1.0.so")
+        set(LIBUSB_SHARED_LIBRARY "${LIBUSB_LIBRARY}")
+        set(LIBUSB_SHARED_LIBRARY_DEST "${CMAKE_BINARY_DIR}/bin/libusb-1.0.so")
+    endif()
 
     # Causes "externals/libusb/libusb/libusb/os/windows_winusb.c:1427:2: error: conversion to non-scalar type requested", so cannot statically link it for now.
     # set(LIBUSB_CFLAGS "-DGUID_DEVINTERFACE_USB_DEVICE=\\(GUID\\){0xA5DCBF10,0x6530,0x11D2,{0x90,0x1F,0x00,0xC0,0x4F,0xB9,0x51,0xED}}")
@@ -37,11 +46,6 @@ if (MINGW)
             "${LIBUSB_PREFIX}"
     )
 
-    # We may use this path for other GNU toolchains, so put all of the MinGW-specific stuff here
-    if (MINGW)
-        set(LIBUSB_CONFIGURE_ARGS --host=x86_64-w64-mingw32 --build=x86_64-windows)
-    endif()
-
     add_custom_command(
         OUTPUT
             "${LIBUSB_MAKEFILE}"
@@ -71,16 +75,24 @@ if (MINGW)
             /bin/cp "${LIBUSB_SHARED_LIBRARY}" "${LIBUSB_SHARED_LIBRARY_DEST}"
     )
 
-    add_custom_target(usb-bootstrap ALL DEPENDS "${LIBUSB_CONFIGURE}")
-    add_custom_target(usb-configure ALL DEPENDS "${LIBUSB_MAKEFILE}" usb-bootstrap)
+    add_custom_target(usb-bootstrap DEPENDS "${LIBUSB_CONFIGURE}")
+    add_custom_target(usb-configure DEPENDS "${LIBUSB_MAKEFILE}" usb-bootstrap)
     add_custom_target(usb-build ALL DEPENDS "${LIBUSB_LIBRARY}" usb-configure)
     # Workaround since static linking didn't work out -- We need to copy the DLL to the bin directory
     add_custom_target(usb-copy ALL DEPENDS "${LIBUSB_SHARED_LIBRARY_DEST}" usb-build)
 
-    # Make `usb` alias to LIBUSB_LIBRARY
     add_library(usb INTERFACE)
+    add_dependencies(usb usb-copy)
     target_link_libraries(usb INTERFACE "${LIBUSB_LIBRARY}")
-else() # MINGW
+
+    if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+        find_package(Libudev QUIET)
+        if(LIBUDEV_FOUND)
+            target_link_libraries(usb INTERFACE "${LIBUDEV_LIBRARIES}")
+            target_include_directories(usb INTERFACE "${LIBUDEV_INCLUDE_DIR}")
+        endif()
+    endif()
+else() # MINGW OR NOT WIN32
     # Ensure libusb compiles with UTF-8 encoding on MSVC
     if(MSVC)
         add_compile_options(/utf-8)