libretro: build fix

gcc9 and the version of msvc19 that the libretro builders use don't
have _mm_storeu_si32. Using _m_cvtsi128_si32 followed by memcpy is
picked up by compilers that support _mm_storeu_si32 as being the same
and they generate the same assembly, so this is no harm to them.

Common/Math/CrossSIMD.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <cstring>
 #include "Common/Math/SIMDHeaders.h"
 
 #define TEST_FALLBACK 0
@@ -244,7 +245,8 @@ struct Vec4F32 {
 	void StoreConvertToU8(uint8_t *dst) {
 		__m128i zero = _mm_setzero_si128();
 		__m128i ivalue = _mm_packus_epi16(_mm_packs_epi32(_mm_cvttps_epi32(v), zero), zero);
-		_mm_storeu_si32(dst, ivalue);
+		int32_t lo = _mm_cvtsi128_si32(ivalue);
+		memcpy(dst, &lo, 4);
 	}
 
 	static Vec4F32 FromVec4S32(Vec4S32 other) { return Vec4F32{ _mm_cvtepi32_ps(other.v) }; }

libretro/Makefile.common

@@ -531,7 +531,6 @@ SOURCES_CXX += \
 	$(COMMONDIR)/UI/View.cpp \
 	$(COMMONDIR)/UI/ViewGroup.cpp \
 	$(COMMONDIR)/UI/ScrollView.cpp \
-	$(COMMONDIR)/UI/PopupScreens.cpp \
 	$(COMMONDIR)/System/Display.cpp \
 	$(COMMONDIR)/System/Request.cpp \
 	$(COMMONDIR)/System/OSD.cpp \