msvc2017: UWP buildfixes

Makefile.libretro

@@ -50,6 +50,7 @@ ifneq ($(GIT_VERSION)," unknown")
 	CFLAGS += -DGIT_VERSION=\"$(GIT_VERSION)\"
 endif
 LIBM := -lm
+LIBS :=
 
 # Unix
 ifeq ($(platform), unix)
@@ -302,7 +303,9 @@ else ifneq (,$(findstring windows_msvc2017,$(platform)))
 		CFLAGS += -DWINAPI_FAMILY=WINAPI_FAMILY_DESKTOP_APP
 	else ifneq (,$(findstring uwp,$(PlatformSuffix)))
 		WinPartition = uwp
-		CFLAGS += -DWINAPI_FAMILY=WINAPI_FAMILY_APP
+		CFLAGS += -DWINAPI_FAMILY=WINAPI_FAMILY_APP -DWINDLL -D_UNICODE -DUNICODE -DWRL_NO_DEFAULT_LIB
+		LDFLAGS += -APPCONTAINER -NXCOMPAT -DYNAMICBASE
+		LIBS += WindowsApp.lib
 	endif
 
 	TargetArchMoniker = $(subst $(WinPartition)_,,$(PlatformSuffix))
@@ -351,8 +354,15 @@ else ifneq (,$(findstring windows_msvc2017,$(platform)))
 	WindowsSDKUCRTLibDir := $(shell cygpath -w "$(WindowsSdkDir)\Lib\$(WindowsSDKVersion)\ucrt\$(TargetArchMoniker)")
 	WindowsSDKUMLibDir := $(shell cygpath -w "$(WindowsSdkDir)\Lib\$(WindowsSDKVersion)\um\$(TargetArchMoniker)")
 
-	#Turns out only the x86 cl.exe can compile for everything, the x64 one only compiles x64
-	VCCompilerToolsBinDir := $(VcCompilerToolsDir)\bin\HostX86
+	# For some reason the HostX86 compiler doesn't like compiling for x64
+	# ("no such file" opening a shared library), and vice-versa.
+	# Work around it for now by using the strictly x86 compiler for x86, and x64 for x64.
+	# NOTE: What about ARM?
+	ifneq (,$(findstring x64,$(TargetArchMoniker)))
+		VCCompilerToolsBinDir := $(VcCompilerToolsDir)\bin\HostX64
+	else
+		VCCompilerToolsBinDir := $(VcCompilerToolsDir)\bin\HostX86
+	endif
 
 	PATH := $(shell IFS=$$'\n'; cygpath "$(VCCompilerToolsBinDir)/$(TargetArchMoniker)"):$(PATH)
 	PATH := $(PATH):$(shell IFS=$$'\n'; cygpath "$(VsInstallRoot)/Common7/IDE")
@@ -466,8 +476,6 @@ endif
 CFLAGS += $(COREDEFINES) $(fpic) $(WARNING_DEFINES) $(DEFINES) $(ENDIANNESS_DEFINES)
 LDFLAGS += $(LIBM)
 
-LIBS :=
-
 ifeq ($(platform), psp1)
 	INCFLAGS += -I$(shell psp-config --pspsdk-path)/include
 endif