os.findExe: do not return binaries in the cwd

lib/pure/os.nim

@@ -141,7 +141,12 @@ proc findExe*(exe: string, followSymlinks: bool = true;
   ## meets the actual file. This behavior can be disabled if desired.
   for ext in extensions:
     result = addFileExt(exe, ext)
-    if existsFile(result): return
+    if existsFile(result):
+      # on Posix ensure we do not yield binaries in the cwd:
+      when defined(posix):
+        if isAbsolute(result): return
+      else:
+        return
   var path = string(getEnv("PATH"))
   for candidate in split(path, PathSep):
     when defined(windows):