Merge #160: cmake: Fix libqrencode optional package support

8fe37b0 fixup! cmake: Add `libqrencode` optional package support (Hennadii Stepanov)

Pull request description:

  Please, refer to `pkg_check_modules` signature: https://cmake.org/cmake/help/latest/module/FindPkgConfig.html#command:pkg_check_modules

ACKs for top commit:
  m3dwards:
    ACK 8fe37b0

Tree-SHA512: 5c7551ee8f7263dd2b5c6b18b76ce846d5798f7d51d955e536fd484069b7f5b739af036c38930553717a5afc6e87ba92ff26709481135c32369d91d5618beb67

cmake/optional.cmake

@@ -189,12 +189,13 @@ else()
 endif()
 
 if(WITH_GUI AND WITH_QRENCODE)
-  if(MSVC)
+  if(VCPKG_TARGET_TRIPLET)
     # TODO: vcpkg fails to build libqrencode package due to
     #       the build error in its libiconv dependency.
     #       See: https://github.com/microsoft/vcpkg/issues/36924.
   else()
-    cross_pkg_check_modules(libqrencode libqrencode IMPORTED_TARGET)
+    include(CrossPkgConfig)
+    cross_pkg_check_modules(libqrencode IMPORTED_TARGET libqrencode)
   endif()
   if(TARGET PkgConfig::libqrencode)
     set_target_properties(PkgConfig::libqrencode PROPERTIES