Fix issue with outputting "static" in GLSL (shader-slang#1006)

This appears to be a regression introduced in shader-slang#1001, and missed because none of our existing tests covered `static const` arrays on the GLSL/SPIR-V targets.

The basic problem is that we cannot output a `static const` definition in GLSL because `static` is a reserved word and not a keyword. Instead for GLSL we just want a `const` array. This change makes the emission of `static` for global-scope constants key on the target language for code generation, and only emit it for HLSL, C, and C++.

This change also adds a test case specifically for running Slang input that has a `static const` array on the Vulkan target.

Author: Tim Foley

source/slang/slang-emit-c-like.cpp

@@ -982,7 +982,20 @@ void CLikeSourceEmitter::emitInstResultDecl(IRInst* inst)
     if(as<IRModuleInst>(inst->getParent()))
     {
         // "Ordinary" instructions at module scope are constants
-        m_writer->emit("static const ");
+
+        switch (getSourceStyle())
+        {
+        case SourceStyle::HLSL:
+        case SourceStyle::C:
+        case SourceStyle::CPP:
+            m_writer->emit("static ");
+            break;
+
+        default:
+            break;
+        }
+
+        m_writer->emit("const ");
     }
 
     emitType(type, getName(inst));

tests/bugs/glsl-static-const-array.slang

@@ -0,0 +1,17 @@
+// glsl-static-const-array.slang
+
+//TEST(compute):COMPARE_COMPUTE:-vk
+
+static const int gData[4] =
+{
+    0xA, 0xB, 0xC, 0xD,
+};
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(0),glbinding(0),out
+RWStructuredBuffer<int> gBuffer;
+
+[numthreads(4,1,1)]
+void computeMain(uint3 tid : SV_DispatchThreadID)
+{
+    gBuffer[tid.x] = gData[tid.x];
+}

tests/bugs/glsl-static-const-array.slang.expected.txt

@@ -0,0 +1,4 @@
+A
+B
+C
+D