Update action to use native bmake if possible

On MacOS, native bmake works fine, refactor the environment to be able to use it.
While here, update to the latests ubuntu version, clang versions.

.github/workflows/cross-bootstrap-tools.yml

@@ -2,9 +2,13 @@ name: Cross-build Kernel
 
 on:
   push:
-    branches: [ main, 'stable/14', 'stable/13' ]
+    branches: 
+      - main
+      - 'stable/14'
+      - 'stable/13'
   pull_request:
-    branches: [ main ]
+    branches: 
+      - main
   workflow_dispatch:
 
 permissions:
@@ -17,22 +21,27 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        target_arch: [ amd64, aarch64 ]
-        os: [ ubuntu-20.04, ubuntu-22.04, macos-latest ]
+        target_arch:
+          - amd64
+          - aarch64
+        os: 
+          - ubuntu-24.04
+          - macos-latest
         include:
-          # TODO: both Ubuntu and macOS have bmake packages, we should try them instead of bootstrapping our own copy.
-          - os: ubuntu-20.04
-            compiler: clang-12
-            cross-bindir: /usr/lib/llvm-12/bin
-            pkgs: bmake libarchive-dev clang-12 lld-12
-          - os: ubuntu-22.04
-            compiler: clang-14
-            cross-bindir: /usr/lib/llvm-14/bin
-            pkgs: bmake libarchive-dev clang-14 lld-14
+          - os: ubuntu-24.04
+            compiler: clang-18
+            pkgs: libarchive-dev clang-18 lld-18
+            llvm-bindir: /usr/lib/llvm-18/bin
+            llvm-ld: /usr/lib/llvm-18/bin/ld.lld
+            # the Ubuntu packaged bmake causes build errors
+            bmake: ./tools/build/make.py
           - os: macos-latest
-            compiler: clang-13
-            cross-bindir: /opt/homebrew/opt/llvm@13/bin
-            pkgs: bmake libarchive llvm@13
+            compiler: clang-18
+            # llvm@19 causes build error
+            pkgs: bmake libarchive llvm@18 lld
+            llvm-bindir: /opt/homebrew/opt/llvm@18/bin
+            llvm-ld: /opt/homebrew/opt/lld/bin/ld.lld
+            bmake: bmake
           - target_arch: amd64
             target: amd64
           - target_arch: aarch64
@@ -51,17 +60,35 @@ jobs:
           brew install ${{ matrix.pkgs }} || true
       - name: create environment
         run: |
-          echo "GITHUB_WORKSPACE = $GITHUB_WORKSPACE"
-          if [ -n "${{ matrix.cross-bindir }}" ]; then
-            echo "EXTRA_BUILD_ARGS=--cross-bindir=${{ matrix.cross-bindir }}" >> $GITHUB_ENV
-          fi
+          echo "CC=${{ matrix.llvm-bindir }}/clang" >> $GITHUB_ENV
+          echo "CXX=${{ matrix.llvm-bindir }}/clang++" >> $GITHUB_ENV
+          echo "CPP=${{ matrix.llvm-bindir }}/clang-cpp" >> $GITHUB_ENV
+
+          echo "XCC=${{ matrix.llvm-bindir }}/clang" >> $GITHUB_ENV
+          echo "XCXX=${{ matrix.llvm-bindir }}/clang++" >> $GITHUB_ENV
+          echo "XCPP=${{ matrix.llvm-bindir }}/clang-cpp" >> $GITHUB_ENV
+          echo "XLD=${{ matrix.llvm-ld }}" >> $GITHUB_ENV
+
           mkdir -p ../build
           echo "MAKEOBJDIRPREFIX=${PWD%/*}/build" >> $GITHUB_ENV
-          # heh, works on Linux/BSD/macOS ...
           echo "NPROC=`getconf _NPROCESSORS_ONLN 2>/dev/null || getconf NPROCESSORS_ONLN 2>/dev/null || echo 1`" >> $GITHUB_ENV
-      - name: bootstrap bmake
-        run: ./tools/build/make.py --debug $EXTRA_BUILD_ARGS TARGET=${{ matrix.target }} TARGET_ARCH=${{ matrix.target_arch }} -n
+
+      - name: show environment
+        run: |
+          echo Running on $(uname -a)
+          echo "CWD = $PWD"
+          echo "GITHUB_WORKSPACE = $GITHUB_WORKSPACE"
+          echo "Using bmake as ${{ matrix.bmake }}"
+          echo Using CC=${CC}
+          echo Using LD=${LD}
+          echo Using XCC=${XCC}
+          echo Using XLD=${XLD}
+          echo Using MAKEOBJDIRPREFIX=${MAKEOBJDIRPREFIX}
+          echo Using NPROC=${NPROC}
+          echo Using EXTRA_MAKE_ARGS=${EXTRA_MAKE_ARGS}
+
       - name: make kernel-toolchain
-        run: ./tools/build/make.py --debug $EXTRA_BUILD_ARGS TARGET=${{ matrix.target }} TARGET_ARCH=${{ matrix.target_arch }} kernel-toolchain -s -j$NPROC -DWITH_DISK_IMAGE_TOOLS_BOOTSTRAP
+        run: ${{ matrix.bmake }} TARGET=${{ matrix.target }} TARGET_ARCH=${{ matrix.target_arch }} -s -j$NPROC kernel-toolchain -DWITH_DISK_IMAGE_TOOLS_BOOTSTRAP
+
       - name: make buildkernel
-        run: ./tools/build/make.py --debug $EXTRA_BUILD_ARGS TARGET=${{ matrix.target }} TARGET_ARCH=${{ matrix.target_arch }} KERNCONF=GENERIC NO_MODULES=yes buildkernel -s -j$NPROC $EXTRA_MAKE_ARGS
+        run: ${{ matrix.bmake }} TARGET=${{ matrix.target }} TARGET_ARCH=${{ matrix.target_arch }} -s -j$NPROC buildkernel KERNCONF=GENERIC NO_MODULES=yes