Find the translator and spirv-val by OS in xlate_smoke.py, so the smoke test runs on Linux.

tools/xlate_smoke.py

@@ -1,4 +1,4 @@
-"""Smoke test for build/xlate/totk_xlate.exe: no game files needed.
+"""Smoke test for build/xlate/totk_xlate(.exe): no game files needed.
 
 Sends one hand-assembled Maxwell fragment shader (writes the constant colour 1.0, 0.5, 0.25, 1.0 to render target 0)
 through --serve, checks the reply, validates the SPIR-V with spirv-val, then sends a malformed line and checks the
@@ -8,6 +8,8 @@ service survives and still answers.
 """
 
 import json
+import os
+import shutil
 import struct
 import subprocess
 import sys
@@ -15,8 +17,9 @@ import tempfile
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
-EXE = ROOT / "build" / "xlate" / "totk_xlate.exe"
-SPIRV_VAL = Path(r"C:\msys64\ucrt64\bin\spirv-val.exe")
+EXE = ROOT / "build" / "xlate" / ("totk_xlate.exe" if os.name == "nt" else "totk_xlate")
+SPIRV_VAL = (Path(r"C:\msys64\ucrt64\bin\spirv-val.exe") if os.name == "nt"
+             else Path(shutil.which("spirv-val") or "/usr/bin/spirv-val"))
 
 PT = 7 << 16  # predicate "always"