Update macOS docs and CI script to use LIBOMP_PREFIX for OpenMP libra…

…ry path

.github/workflows/build.yml

@@ -57,10 +57,10 @@ jobs:
           cd ~/VulkanSDK/latest
           sudo python ./install_vulkan.py
           brew install libomp
-          brew --prefix libomp 
       - name: Build
         run: |
-          cmake -G "Xcode" -DOpenMP_omp_LIBRARY=/usr/local/opt/libomp/lib/libomp.dylib .
+          export LIBOMP_PREFIX=$(brew --prefix libomp)
+          cmake -G "Xcode" -DOpenMP_omp_LIBRARY=$LIBOMP_PREFIX/lib/libomp.dylib .
           cmake --build .
 
   build_iOS:

BUILD.md

@@ -63,15 +63,13 @@ Open **vulkan_sdk.dmg** and install the Vulkan SDK with *System Global Installat
 Install **libomp** from [homebrew](https://brew.sh) using:
 ```brew install libomp```
 
-Find the **libomp** path prefix using:
-```brew --prefix libomp```
-
-Use the **libomp** path prefix to adjust the path for ```-DOpenMP_omp_LIBRARY=``` in the cmake command below.
+Define the **libomp** path prefix using:
+```export LIBOMP_PREFIX=$(brew --prefix libomp)```
 
 Use [CMake](https://cmake.org) to generate a build configuration for Xcode or your preferred build method (e.g. Unix Makefiles or Ninja).
 
-Example of cmake generating for Xcode with **libomp** path defined for homebrew on Apple Silicon:
-```cmake -G "Xcode" -DOpenMP_omp_LIBRARY=/opt/homebrew/opt/libomp/lib/libomp.dylib```
+Example of cmake generating for Xcode with **libomp** library path defined:
+```cmake -G "Xcode" -DOpenMP_omp_LIBRARY=$LIBOMP_PREFIX/lib/libomp.dylib .```
 
 ####iOS
 Navigate to the [apple](apple/) folder and follow the instructions in [README\_MoltenVK_Examples.md](apple/README_MoltenVK_Examples.md)