Add -Cforce-frame-pointers to make the PDBALTPATH test case non-flaky…

… on i686-pc-windows-msvc

.github/workflows/main.yml

@@ -112,13 +112,14 @@ jobs:
 
     # Test that backtraces are still symbolicated if we don't embed an absolute
     # path to the PDB file in the binary.
-    - run: |
-        cargo clean
-        cargo test
+    # Add -Cforce-frame-pointers for stability. The test otherwise fails
+    # non-deterministically on i686-pc-windows-msvc because the stack cannot be
+    # unwound reliably. This failure is not related to the feature being tested.
+    - run: cargo clean && cargo test
       if: contains(matrix.rust, 'msvc')
       name: "Test that backtraces are symbolicated without absolute PDB path"
       env:
-        RUSTFLAGS: "-C link-arg=/PDBALTPATH:%_PDB%"
+        RUSTFLAGS: "-Clink-arg=/PDBALTPATH:%_PDB% -Cforce-frame-pointers"
 
     # Test that including as a submodule will still work, both with and without
     # the `backtrace` feature enabled.