win binary: build zbar ourselves (#6593)

This allows bundling much newer zbar that includes many fixes.
related: #6018

This is largely based on
https://github.com/Electron-Cash/Electron-Cash/pull/1362
https://github.com/Electron-Cash/Electron-Cash/pull/1363
https://github.com/Electron-Cash/Electron-Cash/pull/1365
eda015908e

electrum/qrscanner.py

@@ -27,6 +27,12 @@ import os
 import sys
 import ctypes
 
+from .logging import get_logger
+
+
+_logger = get_logger(__name__)
+
+
 if sys.platform == 'darwin':
     name = 'libzbar.dylib'
 elif sys.platform in ('windows', 'win32'):
@@ -35,25 +41,27 @@ else:
     name = 'libzbar.so.0'
 
 try:
-    libzbar = ctypes.cdll.LoadLibrary(name)
-except BaseException:
-    libzbar = None
+    libzbar = ctypes.cdll.LoadLibrary(os.path.join(os.path.dirname(__file__), name))
+except BaseException as e1:
+    try:
+        libzbar = ctypes.cdll.LoadLibrary(name)
+    except BaseException as e2:
+        libzbar = None
+        if sys.platform != 'darwin':
+            _logger.error(f"failed to load zbar. exceptions: {[e1,e2]!r}")
 
 
-def scan_barcode_ctypes(device='', timeout=-1, display=True, threaded=False, try_again=True):
+def scan_barcode_ctypes(device='', timeout=-1, display=True, threaded=False):
     if libzbar is None:
         raise RuntimeError("Cannot start QR scanner; zbar not available.")
     libzbar.zbar_symbol_get_data.restype = ctypes.c_char_p
     libzbar.zbar_processor_create.restype = ctypes.POINTER(ctypes.c_int)
     libzbar.zbar_processor_get_results.restype = ctypes.POINTER(ctypes.c_int)
     libzbar.zbar_symbol_set_first_symbol.restype = ctypes.POINTER(ctypes.c_int)
+    # libzbar.zbar_set_verbosity(100)  # verbose logs for debugging
     proc = libzbar.zbar_processor_create(threaded)
     libzbar.zbar_processor_request_size(proc, 640, 480)
     if libzbar.zbar_processor_init(proc, device.encode('utf-8'), display) != 0:
-        if try_again:
-            # workaround for a bug in "ZBar for Windows"
-            # libzbar.zbar_processor_init always seem to fail the first time around
-            return scan_barcode(device, timeout, display, threaded, try_again=False)
         raise RuntimeError("Can not start QR scanner; initialization failed.")
     libzbar.zbar_processor_set_visible(proc)
     if libzbar.zbar_process_one(proc, timeout):