Instruct CMake to deprioritise headers in /Library/Frameworks on Mac CI

By setting, CMAKE_FIND_FRAMEWORK=LAST we instruct CMake to not look
for header files inside /Library/Frameworks as a first search path.
This can cause issue when frameoworks like Mono are present on the system,
resulting in CMake unable to find the homebrew library headers.

.github/workflows/checks.yml

@@ -158,6 +158,7 @@ jobs:
         -B build
         -G Ninja
         -D CMAKE_BUILD_TYPE=Release
+        -D CMAKE_FIND_FRAMEWORK=LAST
         -D MRTRIX_BUILD_TESTS=ON
         -D MRTRIX_STL_DEBUGGING=ON
         -D MRTRIX_USE_PCH=OFF