package/flutter-pi: invert dependency logic

Flutter-engine is by name an engine, i.e. a runtime for applications, a
super-library of sorts. As such, it makes more sense for applications to
select flutter-engine rather than to depend on it.

Change flutter-pi to select flutter-engine.

It also brings flutter-pi on par with ivi-homescreen, another embedder.

Signed-off-by: Adam Duskett <adam.duskett@amarulasolutions.com>
[yann.morin.1998@free.fr: reword commit log]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/flutter-pi/Config.in

@@ -1,9 +1,20 @@
 menuconfig BR2_PACKAGE_FLUTTER_PI
 	bool "flutter-pi"
-	depends on BR2_PACKAGE_FLUTTER_ENGINE
+	depends on BR2_PACKAGE_HOST_FLUTTER_SDK_BIN_ARCH_SUPPORTS
+	depends on BR2_PACKAGE_FLUTTER_ENGINE_ARCH_SUPPORTS
+	depends on BR2_HOST_GCC_AT_LEAST_5 # flutter-engine
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_5 # flutter-engine
+	depends on !BR2_TOOLCHAIN_HAS_GCC_BUG_64735 # flutter-engine
+	depends on BR2_TOOLCHAIN_USES_GLIBC # flutter-engine
+	depends on BR2_INSTALL_LIBSTDCPP # flutter-engine
+	depends on !BR2_STATIC_LIBS # flutter-engine, wayland
+	depends on BR2_USE_WCHAR # flutter-engine
+	depends on BR2_PACKAGE_HAS_LIBGL || BR2_PACKAGE_HAS_LIBGLES # flutter-engine
 	depends on BR2_PACKAGE_HAS_LIBGBM
 	depends on BR2_PACKAGE_SYSTEMD # Event loop and dbus support
 	depends on BR2_PACKAGE_HAS_UDEV # libinput
+	select BR2_PACKAGE_HOST_FLUTTER_SDK_BIN
+	select BR2_PACKAGE_FLUTTER_ENGINE
 	select BR2_PACKAGE_LIBDRM
 	select BR2_PACKAGE_LIBINPUT
 	select BR2_PACKAGE_LIBXKBCOMMON
@@ -80,8 +91,22 @@ config BR2_PACKAGE_FLUTTER_PI_TEXT_INPUT_PLUGIN
 
 endif
 
-comment "flutter-pi needs flutter-engine"
-	depends on !BR2_PACKAGE_FLUTTER_ENGINE
+comment "flutter-pi needs a glibc toolchain w/ wchar, C++, gcc >= 5, dynamic library, host gcc >= 5"
+	depends on BR2_PACKAGE_HOST_FLUTTER_SDK_BIN_ARCH_SUPPORTS
+	depends on BR2_PACKAGE_FLUTTER_ENGINE_ARCH_SUPPORTS
+	depends on !BR2_TOOLCHAIN_USES_GLIBC || !BR2_INSTALL_LIBSTDCPP \
+		|| !BR2_TOOLCHAIN_GCC_AT_LEAST_5 || BR2_STATIC_LIBS \
+		|| !BR2_USE_WCHAR || !BR2_HOST_GCC_AT_LEAST_5
+
+comment "flutter-pi needs a toolchain not affected by GCC bug 64735"
+	depends on BR2_PACKAGE_HOST_FLUTTER_SDK_BIN_ARCH_SUPPORTS
+	depends on BR2_PACKAGE_FLUTTER_ENGINE_ARCH_SUPPORTS
+	depends on BR2_TOOLCHAIN_HAS_GCC_BUG_64735
+
+comment "flutter-pi needs an OpenGL or OpenGLES backend"
+	depends on BR2_PACKAGE_HOST_FLUTTER_SDK_BIN_ARCH_SUPPORTS
+	depends on BR2_PACKAGE_FLUTTER_ENGINE_ARCH_SUPPORTS
+	depends on !BR2_PACKAGE_HAS_LIBGL && !BR2_PACKAGE_HAS_LIBGLES
 
 comment "flutter-pi needs GBM, systemd, and udev"
 	depends on !BR2_PACKAGE_HAS_LIBGBM || \