samples/bpf: fix build

JIRA: https://issues.redhat.com/browse/RHEL-70466

Upstream Status: RHEL Only

commit 9ea5b2d945e7d5fe6daffd766520dfb1fb6b5974
Author: Gregory Bell <grbell@redhat.com>
Date:   Wed Apr 2 12:21:58 2025 -0400

    samples/bpf: fix build

    Moving bootstrap bpftool build into a function then pass bootstrap bpftool to
    samples/bpf Makefile instead of rebuilding during the samples/bpf make process.
    If bpftool is not already built then build right before samples/bpf build and
    pass to samples/bpf.
    Always pass vmlinux.h to samples/bpf by setting RPM_VMLINUX_H variable
    depending on current build. If the kernel is built with debuginfo it is
    located at RPM_BUILD_ROOT/DevelDir/vmlinux.h. In the case of tools only build
    it is at DevelDir/vmlinux.h

    Signed-off-by: Gregory Bell <grbell@redhat.com>

Signed-off-by: Gregory Bell <grbell@redhat.com>

Author: Gbell26

redhat/kernel.spec.template

@@ -2220,6 +2220,13 @@ InitBuildVars() {
     fi
 }
 
+#Build bootstrap bpftool
+BuildBpftool(){
+    export BPFBOOTSTRAP_CFLAGS=$(echo "%{__global_compiler_flags}" | sed -r "s/\-specs=[^\ ]+\/redhat-annobin-cc1//")
+    export BPFBOOTSTRAP_LDFLAGS=$(echo "%{__global_ldflags}" | sed -r "s/\-specs=[^\ ]+\/redhat-annobin-cc1//")
+    CFLAGS="" LDFLAGS="" make EXTRA_CFLAGS="${BPFBOOTSTRAP_CFLAGS}" EXTRA_CXXFLAGS="${BPFBOOTSTRAP_CFLAGS}" EXTRA_LDFLAGS="${BPFBOOTSTRAP_LDFLAGS}" %{?make_opts} %{?clang_make_opts} V=1 -C tools/bpf/bpftool bootstrap
+}
+
 BuildKernel() {
     %{log_msg "BuildKernel for $4"}
     MakeTarget=$1
@@ -2953,10 +2960,7 @@ BuildKernel() {
     if [ "$Variant" != "zfcpdump" ]; then
 	%{log_msg "Build the bootstrap bpftool to generate vmlinux.h"}
         # Build the bootstrap bpftool to generate vmlinux.h
-        export BPFBOOTSTRAP_CFLAGS=$(echo "%{__global_compiler_flags}" | sed -r "s/\-specs=[^\ ]+\/redhat-annobin-cc1//")
-        export BPFBOOTSTRAP_LDFLAGS=$(echo "%{__global_ldflags}" | sed -r "s/\-specs=[^\ ]+\/redhat-annobin-cc1//")
-        CFLAGS="" LDFLAGS="" make EXTRA_CFLAGS="${BPFBOOTSTRAP_CFLAGS}" EXTRA_CXXFLAGS="${BPFBOOTSTRAP_CFLAGS}" EXTRA_LDFLAGS="${BPFBOOTSTRAP_LDFLAGS}" %{?make_opts} %{?clang_make_opts} V=1 -C tools/bpf/bpftool bootstrap
-
+        BuildBpftool
         tools/bpf/bpftool/bootstrap/bpftool btf dump file vmlinux format c > $RPM_BUILD_ROOT/$DevelDir/vmlinux.h
     fi
 %endif
@@ -3201,7 +3205,10 @@ pushd tools/tracing/rtla
 popd
 %endif
 
-if [ -f $DevelDir/vmlinux.h ]; then
+#set RPM_VMLINUX_H
+if [ -f $RPM_BUILD_ROOT/$DevelDir/vmlinux.h ]; then
+  RPM_VMLINUX_H=$RPM_BUILD_ROOT/$DevelDir/vmlinux.h
+elif [ -f $DevelDir/vmlinux.h ]; then
   RPM_VMLINUX_H=$DevelDir/vmlinux.h
 fi
 echo "${RPM_VMLINUX_H}" > ../vmlinux_h_path
@@ -3222,8 +3229,13 @@ if [ ! -f include/generated/autoconf.h ]; then
    %{make} %{?_smp_mflags} modules_prepare
 fi
 
+# Build BPFtool for samples/bpf
+if [ ! -f tools/bpf/bpftool/bootstrap/bpftool ]; then
+  BuildBpftool
+fi
+
 %{log_msg "build samples/bpf"}
-%{make} %{?_smp_mflags} EXTRA_CXXFLAGS="${RPM_OPT_FLAGS}" ARCH=$Arch V=1 M=samples/bpf/ VMLINUX_H="${RPM_VMLINUX_H}" || true
+%{make} %{?_smp_mflags} EXTRA_CXXFLAGS="${RPM_OPT_FLAGS}" ARCH=$Arch BPFTOOL=$(pwd)/tools/bpf/bpftool/bootstrap/bpftool V=1 M=samples/bpf/ VMLINUX_H="${RPM_VMLINUX_H}" || true
 
 pushd tools/testing/selftests
 # We need to install here because we need to call make with ARCH set which