tools/bpf: Allow overriding llvm tools for runqslower

tools/testing/selftests/bpf/Makefile supports overriding clang, llc and
other tools so that custom ones can be used instead of those from PATH.
It's convinient and heavily used by some users.

Apply same rules to runqslower/Makefile.

Signed-off-by: Andrey Ignatov <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: rdna

tools/bpf/runqslower/Makefile

@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 OUTPUT := .output
-CLANG := clang
-LLC := llc
-LLVM_STRIP := llvm-strip
+CLANG ?= clang
+LLC ?= llc
+LLVM_STRIP ?= llvm-strip
 DEFAULT_BPFTOOL := $(OUTPUT)/sbin/bpftool
 BPFTOOL ?= $(DEFAULT_BPFTOOL)
 LIBBPF_SRC := $(abspath ../../lib/bpf)