mke2fs: Don't require mke2fs.conf on Windows.

This target doesn't exist on Windows.

Fixes the following error:
build/make/core/main.mk:586: warning: Missing required dependency host_cross_mke2fs.conf from module host_cross_mke2fs defined in out/soong/Android-aosp_walleye.mk

Bug: 7456955
Test: above error no longer present
Change-Id: I278e53488ecfc4f9d5e540a70276344af06ad455
1 file changed