exe: defend test case against msys2 paths

test/exe.cpp

@@ -2,6 +2,8 @@
 
 #include "../exe.hpp"
 
+#include <experimental/filesystem>
+
 
 ///////////////////////////////////////////////////////////////////////////////
 int
@@ -9,7 +11,19 @@ main (int, char **argv)
 {
     cruft::TAP::logger tap;
 
-    auto path = cruft::image_path ();
-    tap.expect_eq (path, argv[0], "identify executable path");
+    // we'd like to compare based on the total path, but systems like msys2
+    // have varying styles of paths and it's difficult to harmonize the
+    // expected and queried values.
+    //
+    // so we compare the filename instead under the assumption that it should
+    // be stable across path styles.
+    auto const query = cruft::image_path ();
+    auto const truth = std::experimental::filesystem::path (argv[0]);
+    tap.expect_eq (
+        query.stem (),
+        truth.stem (),
+        "identify executable path # %!", query
+    );
+
     return tap.status ();
 }