fix: macOS x64 build timeout by using Intel runners and 4-core parallelization (#113)

### Problem
The macOS x64 build was timing out when using `macos-14` runners with
`MAKE_JOB_COUNT=2`, likely due to cross-compilation overhead.

### Solution
- Changed `runs-on` from `macos-14` to `macos-15-intel` to use native
Intel hardware
- Increased `MAKE_JOB_COUNT` from `2` to `4` to utilize all 4 CPU cores
available on Intel runners

### Result
Resolves build timeout issues for macOS x64 builds by eliminating
cross-compilation and maximising CPU utilization.

Tested Build:
https://github.com/nrranjithnr/pkg-fetch/actions/runs/17977769583

.github/workflows/build-macos.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   macos-x64:
-    runs-on: macos-14
+    runs-on: macos-15-intel
 
     strategy:
       fail-fast: false
@@ -43,7 +43,7 @@ jobs:
 
       - run: yarn start --node-range node${{ matrix.target-node }} --arch x64 --output dist
         env:
-          MAKE_JOB_COUNT: 2 # prevent to run out of memory
+          MAKE_JOB_COUNT: 4 # prevent to run out of memory
 
       - name: Check if binary is compiled, skip if download only
         id: check_file