Generating BTF during kernel builds involves building host libbpf, which fails
unless __NR_bpf is defined.

diff --git a/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_32.h b/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_32.h
index 45e32d0..6f6cb88 100644
--- a/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_32.h
+++ b/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_32.h
@@ -348,5 +348,6 @@
 #define __NR_process_vm_writev 348
 #define __NR_kcmp 349
 #define __NR_finit_module 350
+#define __NR_bpf 357
 
 #endif /* _ASM_X86_UNISTD_32_H */
diff --git a/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_64.h b/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_64.h
index 82e1308..550dade 100644
--- a/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_64.h
+++ b/sysroot/usr/include/x86_64-linux-gnu/asm/unistd_64.h
@@ -315,5 +315,6 @@
 #define __NR_process_vm_writev 311
 #define __NR_kcmp 312
 #define __NR_finit_module 313
+#define __NR_bpf 321
 
 #endif /* _ASM_X86_UNISTD_64_H */