[PATCH v2 dwarves] github CI: build/install bpftool from kernel tree

It will be useful for selftests.  With this change on top
of the v5 gcc BTF tag series [1], CI runs succeed where
they previously failed due to absence of bpftool.

Changes since v1:

- need to specify LLVM_OBJCOPY env var for pahole invokations
in pfunct-btf-decl-tag.sh to succeed.

[1] https://github.com/alan-maguire/dwarves/actions/runs/27790591177/job/82238306741

Signed-off-by: Alan Maguire <[email protected]>
---
 .github/scripts/build-kernel.sh  | 3 +++
 .github/scripts/run-selftests.sh | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/.github/scripts/build-kernel.sh b/.github/scripts/build-kernel.sh
index 0a1fd3f..9f11b22 100755
--- a/.github/scripts/build-kernel.sh
+++ b/.github/scripts/build-kernel.sh
@@ -40,3 +40,6 @@ make $buildopts olddefconfig && make prepare
 cat .config
 make -j $((4*$(nproc))) $buildopts all
 
+# Build, install bpftool
+cd tools/bpf/bpftool
+LLVM_STRIP=llvm-strip-${LLVM_VERSION} make && make DESTDIR=${GITHUB_WORKSPACE}/install/ install
diff --git a/.github/scripts/run-selftests.sh b/.github/scripts/run-selftests.sh
index f9ba24e..bb826bf 100755
--- a/.github/scripts/run-selftests.sh
+++ b/.github/scripts/run-selftests.sh
@@ -8,8 +8,10 @@ GITHUB_WORKSPACE=${GITHUB_WORKSPACE:-$(pwd)}
 VMLINUX=${GITHUB_WORKSPACE}/.kernel/vmlinux
 SELFTESTS=${GITHUB_WORKSPACE}/tests
 cd $SELFTESTS
-export PATH=${GITHUB_WORKSPACE}/install/usr/local/bin:${PATH}
+export PATH=${GITHUB_WORKSPACE}/install/usr/local/bin:${GITHUB_WORKSPACE}/install/usr/local/sbin:${PATH}
+export LLVM_OBJCOPY=objcopy
 which pahole
 pahole --version
+bpftool --version
 vmlinux=$VMLINUX ./tests
 
-- 
2.43.5