Test for link time constants

This test exercises link time constants used by modules that are precompiled to SPIR-V.

Work on shader-slang#6524

Author: cheneym2

tests/expected-failure-github.txt

@@ -14,3 +14,4 @@ tests/language-feature/shader-params/interface-shader-param-ordinary.slang.4 syn
 tests/glsl-intrinsic/shader-subgroup/shader-subgroup-builtin-variables.slang.8 (mtl)
 tests/glsl-intrinsic/shader-subgroup/shader-subgroup-builtin-variables-2.slang.3 (mtl)
 tests/hlsl-intrinsic/texture/partial-resident-texture-combined.slang (dx12)
+tests/library/precompiled-spirv-global.slang

tests/library/export-library-global.slang

@@ -0,0 +1,7 @@
+// TEST_IGNORE_FILE
+
+// export-library-global.slang
+
+export static int myGlobalVar = 42;
+
+

tests/library/precompiled-spirv-global.slang

@@ -0,0 +1,12 @@
+//TEST:COMPILE: tests/library/precompiled-spirv-global.slang -o tests/library/precompiled-spirv-global.slang-module -target spirv -embed-downstream-ir
+
+//import "export-library-global.slang";  //This would make the test pass
+
+extern int myGlobalVar; //This makes the test fail
+
+layout(location = 0) out float4 fragColor;
+
+[shader("fragment")]
+void main() {
+    fragColor = float4(myGlobalVar);
+}