Revert "build, qt: Fix Windows cross-compiling with Qt 5.15"

This reverts commit c4be512.

ci/test/05_before_script.sh

@@ -25,6 +25,9 @@ fi
 if [ -n "$XCODE_VERSION" ] && [ -f "$OSX_SDK_PATH" ]; then
   DOCKER_EXEC tar -C "${DEPENDS_DIR}/SDKs" -xf "$OSX_SDK_PATH"
 fi
+if [[ $HOST = *-mingw32 ]]; then
+  DOCKER_EXEC update-alternatives --set $HOST-g++ \$\(which $HOST-g++-posix\)
+fi
 if [ -z "$NO_DEPENDS" ]; then
   if [[ $DOCKER_NAME_TAG == centos* ]]; then
     # CentOS has problems building the depends if the config shell is not explicitly set

depends/packages/qt.mk

@@ -164,7 +164,6 @@ $(package)_config_opts_mingw32 += -no-dbus
 $(package)_config_opts_mingw32 += -no-freetype
 $(package)_config_opts_mingw32 += -xplatform win32-g++
 $(package)_config_opts_mingw32 += "QMAKE_CFLAGS = '$($(package)_cflags) $($(package)_cppflags)'"
-$(package)_config_opts_mingw32 += "QMAKE_CXX = '$($(package)_cxx)'"
 $(package)_config_opts_mingw32 += "QMAKE_CXXFLAGS = '$($(package)_cflags) $($(package)_cppflags)'"
 $(package)_config_opts_mingw32 += "QMAKE_LFLAGS = '$($(package)_ldflags)'"
 $(package)_config_opts_mingw32 += -device-option CROSS_COMPILE="$(host)-"

doc/build-windows.md

@@ -46,16 +46,13 @@ Acquire the source in the usual way:
 ## Building for 64-bit Windows
 
 The first step is to install the mingw-w64 cross-compilation tool chain:
-  - on modern systems (Ubuntu 21.04 Hirsute Hippo or newer, Debian 11 Bullseye or newer):
 
-```sh
-sudo apt install g++-mingw-w64-x86-64-posix
-```
+    sudo apt install g++-mingw-w64-x86-64
 
-  - on older systems:
+Next, set the default `mingw32 g++` compiler option to POSIX:
 
-```sh
-sudo apt install g++-mingw-w64-x86-64
+```
+sudo update-alternatives --config x86_64-w64-mingw32-g++
 ```
 
 After running the above command, you should see output similar to that below.