Split Linux unwind-v3 check into separate test gated on LINUX_ENABLED

Author: aneshlya

tests/lit-tests/apx-win-unwindv3-linux.ispc

@@ -0,0 +1,14 @@
+// Unwind v3 (the "winx64-eh-unwind" module flag) is Windows-only, so on Linux
+// it is never set even for APX-capable targets that enable the EGPR registers
+// (R16-R31) by default. The Windows-side coverage lives in apx-win-unwindv3.ispc.
+
+//; RUN: %{ispc} %s --target=avx10.2dmr-x16 --arch=x86-64 --target-os=linux --emit-llvm-text -o - | FileCheck %s --check-prefix=NO-V3
+
+// REQUIRES: X86_ENABLED && LINUX_ENABLED && LLVM_23_0+
+
+// NO-V3-NOT: winx64-eh-unwind
+
+void foo(uniform int a[], uniform int n) {
+    for (uniform int i = 0; i < n; ++i)
+        a[i] = a[i] + 1;
+}

tests/lit-tests/apx-win-unwindv3.ispc

@@ -12,8 +12,8 @@
 // Non-APX target: no v3 flag.
 //; RUN: %{ispc} %s --target=avx512skx-x16 --arch=x86-64 --target-os=windows --emit-llvm-text -o - | FileCheck %s --check-prefix=NO-V3
 
-// Linux: unwind v3 is Windows-only, so the flag is never set.
-//; RUN: %{ispc} %s --target=avx10.2dmr-x16 --arch=x86-64 --target-os=linux --emit-llvm-text -o - | FileCheck %s --check-prefix=NO-V3
+// The Linux counterpart (unwind v3 is Windows-only) is verified separately in
+// apx-win-unwindv3-linux.ispc, which is gated on LINUX_ENABLED.
 
 // REQUIRES: X86_ENABLED && WINDOWS_ENABLED && LLVM_23_0+