build, qt: Drop unused CROSS_COMPILE variable for Android builds

Since Qt 5.14.0 the CROSS_COMPILE variable always being overridden by
the Qt build system internally.

See upstream commit: c28b881c98fadcd3415370fad2525b558f6b03e4

Author: hebasto

depends/packages/qt.mk

@@ -167,7 +167,6 @@ $(package)_config_opts_android = -xplatform android-clang
 $(package)_config_opts_android += -android-sdk $(ANDROID_SDK)
 $(package)_config_opts_android += -android-ndk $(ANDROID_NDK)
 $(package)_config_opts_android += -android-ndk-platform android-$(ANDROID_API_LEVEL)
-$(package)_config_opts_android += -device-option CROSS_COMPILE="$(host)-"
 $(package)_config_opts_android += -egl
 $(package)_config_opts_android += -qpa xcb
 $(package)_config_opts_android += -no-dbus