libbpf: Fix INSTALL flag order

It was reported ([0]) that having optional -m flag between source and
destination arguments in install command breaks bpftools cross-build
on MacOS. Move -m to the front to fix this issue.

  [0] https://github.com/openwrt/openwrt/pull/3959

Fixes: 7110d80d ("libbpf: Makefile set specified permission mode")
Signed-off-by: Georgi Valkov <gvalkov@abv.bg>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210308183038.613432-1-andrii@kernel.org

tools/lib/bpf/Makefile

@@ -215,7 +215,7 @@ define do_install
 	if [ ! -d '$(DESTDIR_SQ)$2' ]; then		\
 		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$2';	\
 	fi;						\
-	$(INSTALL) $1 $(if $3,-m $3,) '$(DESTDIR_SQ)$2'
+	$(INSTALL) $(if $3,-m $3,) $1 '$(DESTDIR_SQ)$2'
 endef
 
 install_lib: all_cmd