fix FreeBSD/NetBSD CI: install and use gmake for GNU make compatibility

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: henrik242

.github/workflows/build.yml

@@ -28,7 +28,7 @@ jobs:
         with:
           operating_system: freebsd
           version: '14.2'
-          run: make
+          run: sudo pkg install -y gmake && gmake
   build-netbsd:
     runs-on: ubuntu-latest
     steps:
@@ -38,4 +38,4 @@ jobs:
         with:
           operating_system: netbsd
           version: '10.1'
-          run: make
+          run: sudo pkgin -y install gmake && gmake