mksysinfo: change test == to test =

Fixes https://gcc.gnu.org/PR91621

Change-Id: I8289fab15506d25d014b07a4cb62b49dde38d79a
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/194569
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
1 file changed