Make OpenMP optional instead of default dependency

.github/workflows/pr.yml

@@ -72,9 +72,5 @@ jobs:
         with:
           toolchain: ${{ matrix.rust-version }}
 
-      - name: Install OpenMP
-        run: brew install libomp
-        if: contains(matrix.os, 'macos')
-
       - name: Check build
         run: cargo build -F whisper-cpp-log,whisper-cpp-tracing --verbose --examples

Cargo.toml

@@ -23,7 +23,7 @@ hound = "3.5.0"
 rand = "0.8.4"
 
 [features]
-default = ["openmp"]
+default = []
 
 raw-api = []
 coreml = ["whisper-rs-sys/coreml"]