Update CI to use 4 CPUs on Linux and Windows.

.github/workflows/linux.yml

@@ -26,8 +26,8 @@ jobs:
       uses: actions/checkout@v4
     - name: Build
       run: |
-        # Public runners come with 2 CPUs.
-        make -j2
+        # Public runners come with 4 CPUs.
+        make -j4
     - name: Create testbuild package
       run: |
         # Create release directory tree

.github/workflows/win32.yml

@@ -36,8 +36,8 @@ jobs:
     - name: Build
       shell: msys2 {0}
       run: |
-        # Public runners come with 2 CPUs.
-        make -j2
+        # Public runners come with 4 CPUs.
+        make -j4
     - name: Create testbuild package
       shell: msys2 {0}
       run: |