Fix: Use more selectivity when building SSE specific code

See: https://github.com/OpenTTD/OpenTTD/issues/9935

(cherry picked from commit c3f55d53405af04bfe928d9e1a815e06c187ca50)

src/blitter/32bpp_anim_sse2.cpp

@@ -19,6 +19,7 @@
 /** Instantiation of the partially SSSE2 32bpp with animation blitter factory. */
 static FBlitter_32bppSSE2_Anim iFBlitter_32bppSSE2_Anim;
 
+GNU_TARGET("sse2")
 void Blitter_32bppSSE2_Anim::PaletteAnimate(const Palette &palette)
 {
 	assert(!_screen_disable_anim);