libbpf: don't define CC and AR

We are already including tools/scripts/Makefile.include which correctly
handles CROSS_COMPILE, no need to define our own vars.

See related commit 7ed1c190 ("tools: fix cross-compile var clobbering")
for more details.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/Makefile

@@ -14,21 +14,6 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
-# Makefiles suck: This macro sets a default value of $(2) for the
-# variable named by $(1), unless the variable has been set by
-# environment or command line. This is necessary for CC and AR
-# because make sets default values, so the simpler ?= approach
-# won't work as expected.
-define allow-override
-  $(if $(or $(findstring environment,$(origin $(1))),\
-            $(findstring command line,$(origin $(1)))),,\
-    $(eval $(1) = $(2)))
-endef
-
-# Allow setting CC and AR, or setting CROSS_COMPILE as a prefix.
-$(call allow-override,CC,$(CROSS_COMPILE)gcc)
-$(call allow-override,AR,$(CROSS_COMPILE)ar)
-
 INSTALL = install
 
 # Use DESTDIR for installing into a different root directory.
@@ -54,7 +39,7 @@ man_dir_SQ = '$(subst ','\'',$(man_dir))'
 export man_dir man_dir_SQ INSTALL
 export DESTDIR DESTDIR_SQ
 
-include ../../scripts/Makefile.include
+include $(srctree)/tools/scripts/Makefile.include
 
 # copy a bit from Linux kbuild