ci: set the CARGO_BUILD_TARGET to reuse same cache

Corrosion sets the --target flag to rustc which means
that crates are built in the target sub folder. Ensure
that other places that call cargo directly reuse this
same folder by setting CARGO_BUILD_TARGET.

.github/workflows/github-cxx-qt-tests.yml

@@ -269,6 +269,7 @@ jobs:
             clang_format_path: /home/runner/.local/bin/clang-format
             cargo_dir: ~/.cargo
             rustc_wrapper: sccache
+            cargo_target: x86_64-unknown-linux-gnu
           - name: Ubuntu 24.04 (gcc) Qt6
             os: ubuntu-24.04
             qt_version: 6
@@ -289,6 +290,7 @@ jobs:
                 libgl1-mesa-dev
                 libvulkan-dev
                 libxkbcommon-dev
+            cargo_target: x86_64-unknown-linux-gnu
 
           - name: macOS 13 (clang) Qt5
             os: macos-13
@@ -311,6 +313,7 @@ jobs:
             cc: clang
             cxx: clang++
             rustc_wrapper: sccache
+            cargo_target: x86_64-apple-darwin
           - name: macOS 14 (clang) Qt6
             os: macos-14
             qt_version: 6
@@ -332,6 +335,7 @@ jobs:
             cc: clang
             cxx: clang++
             rustc_wrapper: sccache
+            cargo_target: aarch64-apple-darwin
 
           - name: Windows 2022 (MSVC) Qt5
             os: windows-2022
@@ -350,6 +354,7 @@ jobs:
             cc: cl
             cxx: cl
             rustc_wrapper: sccache
+            cargo_target: x86_64-pc-windows-msvc
           - name: Windows 2022 (MSVC2019) Qt6
             os: windows-2022
             qt_version: 6
@@ -367,6 +372,7 @@ jobs:
             cc: cl
             cxx: cl
             rustc_wrapper: sccache
+            cargo_target: x86_64-pc-windows-msvc
           - name: Windows 2022 (MSVC2022) Qt6
             os: windows-2022
             qt_version: 6
@@ -384,6 +390,7 @@ jobs:
             cc: cl
             cxx: cl
             rustc_wrapper: sccache
+            cargo_target: x86_64-pc-windows-msvc
 
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.name }}
@@ -397,6 +404,8 @@ jobs:
         SCCACHE_CACHE_SIZE: 600M
         SCCACHE_LOG: debug
         SCCACHE_ERROR_LOG: ${{ matrix.sccache_log_path }}
+        # Ensure that we share the same target sub folder
+        CARGO_BUILD_TARGET: ${{ matrix.cargo_target }}
 
     steps:
     - name: "Clone Git repository"

CMakeLists.txt

@@ -157,8 +157,10 @@ if(BUILD_TESTING)
     set_tests_properties(cargo_tests cargo_clippy PROPERTIES
         ENVIRONMENT_MODIFICATION "${CARGO_ENV}"
     )
+    # Cargo doc cannot have a target set otherwise it fails
+    # https://github.com/rust-lang/cargo/issues/10368
     set_tests_properties(cargo_doc PROPERTIES
-        ENVIRONMENT_MODIFICATION "${CARGO_ENV};RUSTDOCFLAGS=set:--deny=warnings"
+        ENVIRONMENT_MODIFICATION "${CARGO_ENV};RUSTDOCFLAGS=set:--deny=warnings;CARGO_BUILD_TARGET=unset"
     )
 
     # Ensure test inputs and outputs are formatted