BUILD: makefile: fix expression again to detect ARM platform

I messed up the fix in 67b095e ("BUILD: makefile: fix regex syntax in
ARM platform detection"), I tried it by hand in the shell without "-v"
but left it in the expression. It works on ARM because it only finds
lines starting with '#' but on other platforms it insists for -latomic.

(cherry picked from commit 48e8603a9c3b5b2509511665cb58d3bde8dfdb65)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit f1da16d1506d2022e74338b0b694fdd2248110f8)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed