Convert executable icon to new method

Manually creating an RC file was the Qt 4 way. The Qt 5 way is just
giving it an icon.

When an RC_FILE isn't manually created Qt will attempt to create one. If
there are non-integers in the version number the compilation will crash.

AdvancedSettings_resource.rc is a build artifact on Windows.

.gitignore

@@ -13,4 +13,5 @@ Makefile*
 installer/*.exe
 *.user*
 build_scripts/win/__pycache__
-build_scripts/win/current_build.bat
+build_scripts/win/current_build.bat
+AdvancedSettings_resource.rc

advancedSettings.pro

@@ -5,6 +5,11 @@ DEFINES += ELPP_THREAD_SAFE ELPP_QT_LOGGING ELPP_NO_DEFAULT_LOG_FILE
 
 VERSION = "$$cat($$PWD/build_scripts/compile_version_string.txt)"
 DEFINES += APPLICATION_VERSION=\\\"$$VERSION\\\"
+# Qmake can't handle non-integers in the version string,
+# so we take out anything after the dash.
+SPLIT_VERSION_STRING = $$split(VERSION, -)
+NUMERICAL_VERSION_NUMBER = $$member(SPLIT_VERSION_STRING, 0, 0)
+VERSION = $$NUMERICAL_VERSION_NUMBER
 
 lessThan(QT_MAJOR_VERSION, 5): error("requires Qt 5.12 or higher")
 lessThan(QT_MINOR_VERSION, 12): error("requires Qt 5.12 or higher")

build_scripts/qt/resources.pri

@@ -47,4 +47,4 @@ DISTFILES += \
     src/res/qml/desktop_overlay_page/translation_back_forwards/SteamDesktopTranslationBackForwards.qml \
     src/res/qml/desktop_overlay_page/translation_up_down/SteamDesktopTranslationUpDown.qml \
 
-RC_FILE = src/res/icon.rc
+win32:RC_ICONS += src/res/img/icons/advicon256px.ico

src/res/icon.rc

@@ -1 +0,0 @@
-IDI_ICON1               ICON    DISCARDABLE     "img/icons/advicon256px.ico"