tools/runqslower: Enable cross-building with clang

Cross-building using clang requires passing the "-target" flag rather
than using the CROSS_COMPILE prefix. Makefile.include transforms
CROSS_COMPILE into CLANG_CROSS_FLAGS. Add them to CFLAGS, and erase
CROSS_COMPILE for the bpftool build, since it needs to be executed on
the host.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20211216163842.829836-6-jean-philippe@linaro.org

tools/bpf/runqslower/Makefile

@@ -12,7 +12,7 @@ BPFOBJ := $(BPFOBJ_OUTPUT)libbpf.a
 BPF_DESTDIR := $(BPFOBJ_OUTPUT)
 BPF_INCLUDE := $(BPF_DESTDIR)/include
 INCLUDES := -I$(OUTPUT) -I$(BPF_INCLUDE) -I$(abspath ../../include/uapi)
-CFLAGS := -g -Wall
+CFLAGS := -g -Wall $(CLANG_CROSS_FLAGS)
 
 # Try to detect best kernel BTF source
 KERNEL_REL := $(shell uname -r)
@@ -88,4 +88,4 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(BPFOBJ_OU
 
 $(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
 	$(Q)$(MAKE) $(submake_extras) -C ../bpftool OUTPUT=$(BPFTOOL_OUTPUT)   \
-		    CC=$(HOSTCC) LD=$(HOSTLD)
+		    ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD)