VideoCommon: Define scalar any() and all() functions in GLSL

This fixes bounding box shaders failing to compile under Vulkan, due to
differences between GLSL and HLSL in the return value of vector
comparisons and what types these functions accept. I included all() for
the sake of completeness.

Source/Core/VideoCommon/PixelShaderGen.cpp

@@ -372,6 +372,16 @@ void WritePixelShaderCommonHeader(ShaderCode& out, APIType api_type,
             "int3 iround(float3 x) {{ return int3(round(x)); }}\n"
             "int4 iround(float4 x) {{ return int4(round(x)); }}\n\n");
 
+  // GLSL's any() and all() only accept vector types, while HLSL's also accept scalar types. We're
+  // adding these for convenience because while vector comparisons return a bool scalar in GLSL,
+  // allowing the results to be used directly in an if statement, they return a bool vector in HLSL,
+  // necessitating the use of any() or all() to reduce it to a scalar.
+  if (api_type == APIType::OpenGL || api_type == APIType::Vulkan)
+  {
+    out.Write("bool any(bool b) {{ return b; }}\n"
+              "bool all(bool b) {{ return b; }}\n\n");
+  }
+
   if (api_type == APIType::OpenGL || api_type == APIType::Vulkan)
   {
     out.Write("SAMPLER_BINDING(0) uniform sampler2DArray samp[8];\n");