impureWithCuda: fix gcc version (#2990)

* impureWithCuda: fix gcc version

* trufflehog: do not fail on unverified results

.github/workflows/trufflehog.yaml

@@ -10,9 +10,11 @@ jobs:
   trufflehog:
     runs-on: ubuntu-latest
     steps:
-    - name: Checkout code
-      uses: actions/checkout@v4
-      with:
-        fetch-depth: 0
-    - name: Secret Scanning
-      uses: trufflesecurity/trufflehog@main
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Secret Scanning
+        uses: trufflesecurity/trufflehog@main
+        with:
+          extra_args: --results=verified,unknown

nix/impure-shell.nix

@@ -94,8 +94,18 @@ mkShell {
     ( cd clients/python ; python -m pip install --no-dependencies -e . )
   '';
 
-  postShellHook = ''
-    unset SOURCE_DATE_EPOCH
-    export PATH=$PATH:~/.cargo/bin
-  '';
+  postShellHook =
+    ''
+      unset SOURCE_DATE_EPOCH
+      export PATH=${cudaPackages.backendStdenv.cc}/bin:$PATH:~/.cargo/bin
+    ''
+    # At various points in time, the latest gcc supported by CUDA differs
+    # from the default version in nixpkgs. A lot of the dependencies in
+    # the impure environment pull in the default gcc from nixpkgs, so we
+    # end up with the CUDA-supported gcc and the nixpkgs default gcc in
+    # the path. To ensure that we can build CUDA kernels, put the CUDA
+    # first in the path. It's a hack, but it works.
+    + lib.optionalString withCuda ''
+      export PATH=${cudaPackages.backendStdenv.cc}/bin:$PATH
+    '';
 }